This Week's Stupid Customer

Yesterday at work I had a strange request from one of the girls on register. We get a lot of customers who apparently are on expense accounts or some nonsense because they're always asking for receipts to record their purchases. Fair enough. But yesterday Poy asks me if she can modify the contents on one of the receipts. I'm pretty sure it can be done, but it's involved and we never have enough people on shift to actually complete our real work without me pissfarting around with the touch screens for five minutes. So I asked what the problem was.
"I accidently pressed the ten dollar button instead of the five dollar button."
"What? You gave her the right change yeah?"
Then Poy's voice drops to this tiny whisper.
"But it says the wrong amount on the receipt."
I looked at the woman, who woulda been in her forties, and just sorta dropped my jaw but didn't say anything. I asked to look at the receipt then explained to her that the slip shows the correct amount of money spent, regardless of how much she actually gave us. She looked at me like she thought I was lying to get rid of her, but left without saying anything. Seriously.
Poy giggled about it after the woman was gone though. You know, I thought if someone was smart enough and had enough responsibility to have an expense account that they'd be able to... you know... count to ten. What the hell?