@valleyforge I'm not sure its either of those to be honest. I think it has more to do with the fact that it would devalue the money supply. A penny is worth more than a penny in terms of raw material, many people keep huge quantities of pennies for their intrinsic rather than implied value.
In addition it means rounding loss for the government on things like taxes. If you buy 1.05 in stuff and tax comes to 0.19 (random numbers) you'd only be able to pay 0.15 in sales tax and the government would have lost out on nearly 25% of their tax in that particular transaction.
Sorry i didnt mean to post that last comment, you are right, even in the USA.. what I meant to say (but apparently sent it before I finished though I dont recall sending) was:
I thought sales tax always rounded down when I said what I did. After your comment I looked it upa nd you are right, it uses normal rounding rules.