The Wall Street Journal's John Fund makes the case that the US should emulate Canada, Australia and New Zealand and eliminate the penny:

Pennies are more of a burden than a help to us. This year, the U.S. Mint will churn out 4.3 billion of them, more than twice the annual output of all other coins combined. Because the penny costs more than a cent to produce, the Treasury loses more than $100 million per year on the coin’s production. Production is up in part because of hoarding, and in part because more and more people are throwing them in jars or drawers and never taking them out again. Few people now bother to pick up a penny when they see it on the street. It’s simply not worth the effort.

So why does the penny still exist? That $100 million goes to somebody, zinc producers for example, and those particular somebodies are naturally greatly attached to their taxpayer-provided income.

Which means that the penny retains one final function: the length of time it takes the U.S. to follow Canada's example is the measure of the greater power of special interests within the American political system as compared to the parliamentary democracies elsewhere in the English-speaking world.