Funny thing happened to me with this situation.
I was at Target lately, and I bought something that came to a total of $21.37. I was at one of those self check-outs, and when i was done with my transaction, I put the money in. It started to say that i needed to put more in, so I did (just to let ya know, I'm not the brightest lightbulb in the closet). So i kept putting money in until finnaly it stopped. I put a grand total of $68.25 in, so I tried to call a manager over. Suddenly, the thing starts to pour out change and give dollar bills out. I flipped out, and fell over. Finnally, some employees came over to shut it off..
So, when I got my money back, I ran as far away from the matchines as fast I could and waited in Starbucks for my mom to come out. When I got there, I wanted a moca-frappachino, so I took the money out, and I found a fifty! I couldn't return it, because I was so scared to go back in there, so I donanted it to the Pecto next door.
I'll never use another Self checkout again..