I too have found squashed pennies in $50 bags,I just shake my head while putting them aside,wondering how in the world... I think my best one is of NY City
Hey - I found one a couple of days ago with my metal dector down at the beach. It was for the CN Tower in Toronto. It wasn't there too long as it was still bright & shiney. My best find of the year for that location! I guess with all the steel Canadian penny's the machines that squish the penny's are all in danger or severe damage to thier dies.
I think that they do go throught the counters. I don't think that the tellers throw them in.
I do know that the tellers at one bank throw in any coins that are stuck on the magnet. This is how I ended up with 50+ steel wheats out of one bag before.