[DerekL]

Most stores in the US don't include sales tax in the listed price, but some do. Examples include vending machines, Starbucks and other coffee shops (but not usually locations inside book stores and supermarkets), and concession stands at concerts, sporting events, and fairs. They probably do it because they don't want to deal with pennies. Concession stands often go further and use whole dollar amounts, since the prices are high anyway.

IIRC, some post office vending machines will take pennies, because they can sell stamps one at a time.

[blahedo]

When I was in grad school there was a pizza-by-the-slice place where all prices were tax-included and an exact multiple of 25c. The only coins in their register were quarters. If you gave them any other coin, they counted it out and dumped it in a jar next to the register. A manager claimed that it was way more efficient and easy to count that way (and throughput mattered a lot during busy times). It also meant that a large percentage of the time the customers had exact change counted out before they even got to the register, which meant they didn't even need to make change and throughput increased further.