However in the SHTF situation there will be plenty of copper in abandoned houses (wires & pipes) and who will need nickel when the industry is deader than a common doornail?
If I were holding a loaf of bread, I'd be willing to exchange it for a good that is just as useful to me as the bread is to you. That could be some other necessity; most likely - water, ammo, gasoline, in that order.
I would accept a coin only when I know that it will be accepted, willingly or under the force of law, anywhere I go. Today both the law and the will help me to pay with US dollars. After SHTF the law will be nonexistent, so only the will remains.
But for anyone to take a common coin he needs to know its true value. How is that determined? In human societies the value of a coin is controlled by availability of such a coin. Only kings made gold coins, for example, and there were very few of those since gold is rare. But nickels ... what will happen to coins in banks' vaults after the SHTF day? They stay there, since nobody at the bank will even think once of taking them elsewhere (and where?) So if you need coins ... you just walk into an abandoned bank and take what you want. Some gangs will even walk into banks that aren't abandoned yet, and make them abandoned. The supply of nickels in banks and stores greatly exceeds anything that you can buy today, and it can be had for free after the SHTF day.
All in all, IMO only necessities will be a good currency, at least for a few years.
I encourage everyone to stockpile necessities, first...I already have all I can store/use.
When TSHTF, bring your gold, silver and copper to me...I'll give you some food for it.