Before I write my opinions, I just want to point out that one of the links given by another poster giving information about this issue had a lot of very good information that is well worth reading through. The post had 2 links and I think the top one was the most informative. So if you missed it you may want to go back and take another look.
As several have said she is 5 and her lying is normal behavior. She probably does not have a full concept of truth, lies, reality, and fantasy, even if you have explained it to her. Some of it is probably an attempt at attention. Negative or positive attention are probably not at the top of her concerns, just attention. She may even think her lies will result in some positive attention if they are believed, or if she believes them. Buy the way, if she says something that isn't true but believes it is true then it is not a lie. Lies are intentional. At 5 things in the world can be very different then they appear to us, so don't assume she has a good concept of what she is doing in your eyes.
I told my daughter when she was about 2, about lies, truth, mistakes, accidents, and the similarities and differences between them. I discuss this with her frequently and also give her example situations and ask her if what I described was a lie, the truth, or a mistake. I do this fairly regularly. I also let her know that lying isn't right, that it hurts, others, makes those lying seem untrustworthy, and will make her feel guilty. She still lies at times, sometimes more than others. But I realize that it is probably either because she wants to sound important, wants to tell creative stories (this is a good thing in my opinion), wants more attention, or is afraid of getting in trouble for the truth. I think you need to try to asses why they are lying, for each situation and react for that situation. If I think she just wants to sound important, I may tell her that it sounds like she is stretching things a bit. If she wants to tell stories I just try to explain to her that it's ok to tell stories but that she should let others know that it's a story, not real, or she can say she made a mistake if she said it was true before, even though it wasn't. If she continues to insist the story is true, then I usually tell her that it doesn't sound right or it sounds like she's stretching the truth. If I think it's an attempt at attention for something I don't want to give attention for, I may say something like sure, right, or I don't think so, then I stop talking to her and maybe even go into another room to do something else. If she is trying to avoid trouble, repremand, or dissaproval, then I try to explain that she needs to be honest, that lying will make things worse for everyone, and it is ok to change her mind about what she said. Then I remind her that lying isn't good, it hurts her and others, and that her and God know the truth and she should consider that.
I usually try to keep my responses short and simple, with very little reaction to keep off some of that attention she wants. The only time I might give a bit more attention to her lie is if I think she is saying hurtful things, or blaming others, then I try to give that more direct attention in pushing the idea that her lies are being hurtful.
The other thing I do is try to notice the good things she does, and honesty she uses and let her know that I really admire that, and explain why her actions were good, helpful, etc. Find lots of those positives, those things that make you proud, those things she really tried hard on, things she's improved on, trouble she's abstained from and really let her know how you feel and that those are real accomplishments. You don't have to go overboard, you don't need forced praise that hasn't been earned, or isn't genuine, but you need real genuine praise, cause most kids can tell when you are just faking it or going through the motions. Plus, that real genuine, prideful praise is so much better then not so genuine praise, for you and for her.
I think buy drawing very little attention to the lies, and buy giving positive attention and praise to the positives, that should automatically give her attention she's looking for while reducing her desire to draw attention to herself buy lying.