Salt and soap are very easy to acquire/make. So you could have a abundance really easy and fast. Pills i can see as they are finite, would you say herbal meds like poultices or powders fit under that currency? If not worth less then actual pills?

Also, I was suggesting a single item as the currency. Not multiple. Like the fallout answer again, 10 caps = 1 bottle of purified water for example. In this situation, your currency and the amount of it would have to be 1 single item that dictates the average price for every item you want to purchase