If you try to short me it'll hurt your tip.

Its interesting you go through all that, I've worked in retail and one of the things we used to do was round down the price so people didn't have to worry about change. If something came to $15.30 or something similar we would call it $15 even and customers would think you did them a favor. In reality 30 cents wasn't usually anything since we probably paid like three or four dollars for the item. People don't want to have to count their change to make sure its right and it would appear foreigners try take advantage of the "lazy or stupid american" far more often then you'd like.

For me after a few years working in a gas station out of high school I learned to count backwards on change so its actually more of a second nature thing to me to know exactly how much I'm getting back before they've opened the till. In your case do like my grandpa would do, carry a change purse and enough ones and fives so that you always had exact change.

Also considering what part of the world your in, I don't see why you couldn't apply my retailer rule the other way around, they ask you for some weird price, round it down reasonably and tell them you'll give them that much. I betcha they'll bite, when possible everyone likes to haggle, see yards for a fine example of this, it gives them the feeling they are in control and a sense of satisfaction when they've made a deal.

see yard sales :P

Traveling twice to Romania this year, I noticed there that usually your total is rounded up or down to the closest unit. That way shops and people only handles bills and no coins (the smallest bill (one leu) is about $0.3).

I used to work in my family's shop, and at least once or twice I accidentally gave too much money. Luckily, the customer is nice enough to point it out and return the cash.

What's more aggravating is when a customer would lie and say they gave me a larger bill like a $20 when it was really a $10. We had a rule that we always give the change back first before putting the cash into the register because of this. And I also learned to do mental math pretty quickly.

Funnily enough it has only happened to me once in my life, and it happened in Australia. The meal was $8, I paid with a $10 note, and received a $20 note in the change. Being the gentleman that I am (some may call this stupid), I gave them the change back. However, it took me about a minute to explain that they gave me TOO much change, they just thought I was complaining that I got underchanged!