I usually make it a point to have a “comfortable” amount of cash in my wallet. I define comfortable as in the $20-$50 range. Enough so that I can stop at the store for a couple of things on the way home and not have to whip out the credit card. Right now I’m at $32.
I’ve noticed some will tend to have next to no cash on a regular basis (regardless of their financial situation), and others will tend towards the extreme (I used to work with a guy who kept a grand on him “just in case” he happened to be passing the casino).