What do you do with foreign coinage that gets mixed in with your country's currency?

I frequently find Canadian pennies mixed in with change I’m given here in the U.S. I never know what to do with them, because I feel like I shouldn’t knowingly try to pass off invalid currency. I’m weird that way.. others probably don’t care.

I’m curious as to what other people do with the random foreign coins they get mixed in with their change. Do you throw them away, save them, cash them in, make art, etc.?