I would buy these

But what about the machines at zoos and museums that smash pennies? They deface coins in such a way that they're unusable.

I could be wrong I thought they were starting to force them to stop but I am not that educated on it this is just what i heard.

This is covered in 18 USC 331. It says that whoever fraudulently alters coins is guilty of a crime. The key word there is "fraudulently." If you alter a coin with the intent of defrauding somebody, you're guilty of a crime. If you alter or destroy a coin you own for reasons other than committing fraud, then you're just wasting money.

ok thank you my bad i misread it

Now a days those machines actually just store your coins and give you the pre made crushed "penny". My local zoo charges a quarter and gives you the thing