Sounds like you got screwed twice. Your employer (neither of them) have a right to make you pay for what happened. If your drawer is short several times they might be able to get away with it, but if it's short only once and it's not a lot of money, they cannot force you to pay it. Same when you were a waitress. You cannot stop someone from walking about on their tab, especially if you are helping out other customers. Your boss had no legal right to force you to pay for their tab.