When I was in the United States in January (Hawaii, Nevada, Utah, Arizona and California), I usually paid for my purchases on my Visa card, however sometimes I would pay cash.
The thing is in Australia, that our tax system is nationwide (ie tax does not vary state to state) and that it is all ready included in the price, i.e a sandwhich is $2.20 all ready had the 10% tax included in the price. So I would go to a shop, see a price of an item and prepare my money for the product (which took ages because all your bills are virtually identical).
I'd then get to the counter only to be informed that the product was x amount more because a) I'd forgotten that the tax was not included or b) I had added on another states tax amount, the result being I had to fiddle around for a while getting my additional monies together.
Some staff and servers were friendly, however the majority were quite rude, rolling their eyes and sighing, as would some of the people behind. Having worked in shops and food service before, I know how annoying it is when someone purchases an item, waits for it to be rung by the staff AND THEN get correct money/card out, but come on!
a) It was obvious I was a tourist- strong accent (a mixture of Australian, British and continental European), a tourist money wallet around my neck and the fact that many times I had an Australian passport in my hand! On top of that, I explained that I was not from the US and apologised for my error!
b) I had cash in my hand, coins and notes which I had prepared all ready, so it was not like I had been waiting in line talking on my mobile phone, to friends or the like.
Overall it was an awesome trip and people were friendly, especially the staff of Hot Topic in Santa Ana mall and basically the entire population of Hawaii, but just remember! Be nice to your tourists, otherwise I'll have to go Russel Crowe on your arse!