I will never understand this. You think if SHTF the grocery and mall are going to have a weight and measure scale where the credit card machine uses to be?
Guns ammo and stored food will be all that matter till a new government is formed and a new currency is created.
Also... I dont think this will happen.
there will still be bartering, and precious metals will retain some value. but its not like the qwik-e-mart is going to have slushies.
You will have to barter with farmers or other good producers. They are going to want something of value, and precious metals are about the best you can come up with. Ammo would be a good alternative, but its heavy and its not worth **that** much.
The ultimate would be cigs. And diet coke.
But this isn't going to happen anytime soon, and if it does we will have plenty of clues. It could have happened in 2008, but we dodged that one with a hearty gov't response. I don't see them failing to do it again, if the need arrives.