What is it for? Selling?

Shooting, only seems to work in single shot guns.

Yes, but they don't seem to have any effect over standard slugs, though I did notice that they have a high value.

Wasting money.

I always thought it was amusing to shoot those legion bastards with it very funny, imo.

"You can have your coins back, I don't need them." BOOM

Exactly B)

Hahahaha. More than I though of such a deed I see

They have a high value, so I just sell them. Unless I need the powder for other ammo.

I believe it's a reference to the Billy the Kid myths. One of the Sheriffs who held him for a while used a shotgun with a 20 dollar load (a roll of dimes in each barrel, replacing the shot in the shells). When he escaped, he killed the Sheriff with his own 20 dollar load.

They tested this on the History channel a while back, the dimes were useless, they fired at a pig carcass with clothes on it, the dimes just bounced off.

If you've ever seen the film Young Guns 2, this scene is played out.