I don't know of any charts specifically. Overall, I think it depends on the type of NPC and the situation you're having the players find them in.
A goblin raider who cannot trust his fellows not to steal his money and who doesn't have a good hideyhole laid out somewhere -- everything is on him.
A farmer out in the field working -- nothing at all.
A laborer around town -- enough for a meal and/or a pint or two at the pub.
A merchant traveling to make a purchase -- enough to make that purchase, which may be quite a bit of money, but then there will be guards hopefully. (One the way back, they have the goods, so that's wealth too.)
I always try to think about what they'd logically be carrying. I don't figure most people carry around much money unless they are planning to need it or unless they have no safe place to keep it. The rural NPC is probably better off burying their stash under a fence post than carrying it around where it could be stolen since there's probably nothing to spend it on during their normal day anyway. An urban NPC would carry enough coins to complete they're likely business. Those humanoid non-human NPCs like orcs, goblins, and ogres might carry the shineys or hide them, depending on how safe they think hiding it would be; it's not like they can walk into a store with the coins.
Of course, unless they're raiding humans, my non-humans and monsters don't have little or no coinage. Their wealth is in other things. I mean, really, where does an owlbear get a pile of coins, unless maybe he's been eating adventurers.
