If he gave them a million pennies to pay for a candy bar, I'm sure they would accept them. They would just give him almost a million pennies back in change! :)

>I was not aware that ANY U.S. merchant (let alone the mint) can legally refuse to accept legal forms of tender. I think there is an old law somewhere (leftover from the civil war era when all merchants had to accept the only legal forms of tender following the war) that states they must. Technically, he should be able to buy a candybar and give all pennies as legal tender and get change back (albeit a lot of change).