WASHINGTON - American consumers have shown about as much appetite for the $1 coin as kids do their spinach. Congressional auditors say doing away with dollar bills entirely and replacing them with dollar coins could save taxpayers some $4.4 billion over the next 30 years. Vending machine operators have long championed the use of $1 coins because they don't jam the machines, cutting down on repair costs and lost sales. But most people don't seem to like carrying them. In the past five years, the U.S. Mint has produced 2.4 billion Presidential $1 coins. Most are stored by the Federal Reserve, and production was suspended about a year ago.