Wow, you really sound irate.
Maybe you need to try another route.
How about rewarding them for telling the truth?
I don't mean necessarily material rewards (boy, could that ever blow up!). But make sure they get the attention they want for being truthful, not for being untruthful. "Jennie, thank you so much for telling me the truth about the broken toy. I appreciate it so much. You are some smart girl!" Make it short and sweet, but very positive and - need I say? - truthful.
If Jennie broke her brother Ralph's toy, take her aside *privately* and make arrangements with her about asking her brother's forgiveness and making things right somehow. Rewarding should be public; chastising should be private.
I have learned from experience that telling a child what a liar he/she is actually encourages him/her to lie. Children tend to live up to what the grownups say about them.
If something happens and you don't put the kids in corners but just clean it up, they might be shocked! They might ask you if you care about who did it. Then you might say, "Of course I care. I hope you all will tell me the truth about it." Then go on cleaning up the mess. As has already been mentioned, purposely broken toys within the family don't need to be replaced. "Too bad - it looked like a nice one. Well, that's the way it happens when folks work hard at breaking things." No lectures. They'll get the point.
If you consider the matter, you want them to be truthful because it's the right way to be, not just because Mama is going to be furious at them. You want to send them the message you want them to receive.
Suppose the toy belongs to someone outside the family, and really does need to be replaced? Replacing something broken is not a punishment; it's a reasonable, just consequence. "Thanks for telling me about that broken car. You know, Timmy ought to be given a car to replace the one that you broke. We'll find out how much it will cost, and I'll help you with the money if it's too much for your piggy bank. That's the way real grownups make things right."
This all may seem pretty mushy. But you want to make it clear to your little ones that truth-telling will be honored (even if there are consequences) and it has nothing to do with Mama's anger. Young children don't have all that straightened out in their heads yet.