Flip of the coin delivery stories ?

I had a delivery to this sweet old lady. It was the first time she ordered from our shop. Her order was cash for around 25 dollars. She hands me two bills, in the reflection of my headlights off her slider door, i could see she handed me a twenty and a hundred dollar bill. I asked her if she'd like change back, She happily replied no, keep the change. I asked her if she's sure, she's getting mildly annoyed with this line of questions by now but says yes again. I ask her if she's aware she handed me a hundred dollar bill. The shock that crosses her face, she absolutely did not realize, she thought she grabbed a ten and twenty. I give her back the hundred and she comes back with another twenty and sure about no change this time. She's a fairly regular customer now.

Another order, about 65 bucks, guy gave me a wad of twenties, no change back. Got around the corner from his house and realized it was 5 twenties, called him real quick, explained that i don't think he intentionally meant to hand me the fifth one and i didn't get far if he needed it. He said i was right but because of my honesty, dont worry about it and keep it. He orders regularly now as well.