Remy Melina shows how ending a retail price with "9" works for more than just the cents column:
[MIT professors] Anderson and Simester illustrated by asking a national clothing catalog to increase the price of one of its dresses. "You'd generally expect demand for an item to go down as the price goes up," Anderson and Simester wrote. "Yet in our study involving the women's clothing catalog, we were able to increase demand by a third by raising the price of a dress from $34 to $39. By comparison, changing the price from $34 to $44 yielded no difference in demand."
(Hat tip: David Pescovitz)