The average annual production of $1 notes from 1980 - 2009 was 3.5 billion. The average lifespan of a $1 note is only 21 months. The average lifespan of a coin is 30 years. An April 7, 2000 Government Accountability Office (GAO) report stated that the government seeks to keep roughly 7.5 billion $1 notes in circulation. The cost of minting 7.5 billion $1 coins at $0.12 per coin is $900 million. The number of new $1 coins minted annually to replace those being destroyed would be far fewer than the 3.5 billion annual note production.
Pennies are little more than a nuisance. Reports as recently as 2008 put the cost of producing one penny between $.012 and $.017. Although the cost to produce a penny fluctuates, it is reasonable to assume that, with inflation, the cost will remain at or above the value of the coin ($.01). If the penny is eliminated and goods are priced in nickel increments (with taxes rounding to the nearest nickel), the resources used to produce pennies can be used to defray the cost of the increased production of the $1 coin.