Keep The Change
Parents ask their kids to do chores all the time and most even reward them in small ways to encourage them. This OP’s mother would send him grocery shopping pretty often and in return for his services, he was allowed to keep the coin part of the change.
He quickly figured out that he could just ask the cashier for rolls of quarters whenever he was getting change. He took advantage of this loophole for quite some time before finally confessing to his mom in his ’20s. His mother couldn’t help but be amused by her smarty-pants child. Honestly, we’re impressed too.