Not used a coin or paper bill for several years now. It’s now at the point where I don’t know what the most common bills and coins look like since they were cha

Not used a coin or paper bill for several years now. It’s now at the point where I don’t know what the most common bills and coins look like since they were changed a few years back and I have never owned most of them. I should keep cash as a backup just like I keep some canned food, but I wonder how society would work in that scenario when many stores don’t have cash registers, many bank offices don’t allow cash deposits and so on. The US would be far more resilient in that situation.