Well, I just did my good deed for the day.
I was just at the store, and the cashier gave me $10 too much change. My change was supposed to be $10.04, and he handed me what, initially, looked like two $5's and four cents. I took it, crumpled it up, and stuffed it in my pocket. Once I got home, I pulled it out to straighten and fold the bills to put them in my wallet, and that's when I found the $10 under the two fives.
Yes, I promptly went back and returned it to that cashier, with a discreet explanation. Would have been so easy to just say "Too bad, so sad!", but, I just couldn't, even though I really didn't feel like making that trip again.
When I was a manager at The Disney Store, if a drawer was off (under or over) by $5 or more, we had to fill out and file a till discrepancy report, and call (leave a message) for the District Manager.
Unfortunately, It happened way more times than you might think. All of us had drawers off from time to time, but, fortunately, the most I ever ( I say "I", but, we really don't know who it happened with, 'cause it was the Holidays and our SM had been instructed to suspend till counts between CM register shifts 'cause it took too long) was $0.75.
Sooo much stuff I coulda' bought with that $10.00, too...!!!