Having just had a discussion regarding banning the U.S. penny, I thought I'd do a little research. It's astounding just how much time and effort has gone into the debate:
And really, all I can contribute is that the phrase "a penny for your thoughts", if we really to eliminate the penny, might be more accurate for what we usually intend when we say that. And how about the sales pitch: "for just pennies a day"? And what about "penny pinching" as a useful phrase?
Gosh - without the penny, many colloquialisms will also disappear. Just hope we're ready for that.