Culture File 6:
Because American dollar bills are all the same color and the same size, store clerks often check by saying «Out of (twenty)» when you give them a bill.
In the U.S.A., every state has a state tax (between 5% and 9%). This tax is not shown in the price. It is added to the total at the cash register. So if you buy something at $6 in a state with 7% tax, the price you pay is $6.42.
In Europe, part of the price is VAT (Value Added Tax), which was 17.5% in the U.K. in 2003. This tax is already included in the price. If the price tag shows £6 or €6, this is what you pay at the cash register.