Depends on the goods.
To tie it into teh real world for a bit, Tide detergeant has popped up as teh drug currency of choice. It's widely available, purchases aren't tracked or restricted, it's a commodity that everyone needs, and it's easy to check out for forgeries. Also, it stores well, so you can warehouse it without fear of depreciation... mice aren't going to eat it, for instance.
They keep busting drug dealers who have hundreds of containers of teh stuff as it's turned into a shadow economy all of itself. Since you can buy drugs with it, you can buy things from people who GET drugs, so, for example, you can trade 'em for guns, as a bribe for helping out, sexual favors (Well, from certain classes of prostitute only), and so on.
The economy's pretty damn organic. It'll find a way to keep commerce flowing.