To be fair, we only have four types of coins in common circulation. Some areas of the country still use the 50-cent pieces and the $1 coins (very large cities such as NYC and Boston love the $1 coins as change for subway passes!), but the majority of places that I've visited in the States use only 1c, 5c, 10c, and 25c coins.
The situation is worse in Canada, in the UK, and in countries that use the Euro. They've got 1c, 2c, 5c, 10c, 20c, 50c, $1, and $2 coins (replace c with p and $ with Pound or Euro, as necessary). The situation with bank notes is also quite worse.