There have been some nice answers so far. Another important detail:

If poor people deal with the cash economy, the smallest coins must be suitable for their needs. Imagine the copper piece (*cp*) is the smallest unit, and a casual farm worker gets paid 1 *cp* per day. That guy couldn't take a day's earnings and take some of it to the cobbler to mend his shoes, some to the inn for a place to sleep, and some to a tavern for beer and a pot of porridge. 2 or 3 *cp* per day are slightly better, but still not good.

Perhaps it would be possible to pay that worker 6 *cp* per week, and the inn would offer room-and-board for a week for 4 *cp*. That allows two single-*cp* purchases per week.

Two options :

- Make those copper coins smaller. A casual worker earns approx. 10 *cp* per day. Most of that goes for food and shelter, but there is 1 or 2 *cp* left for other expenses. Other prices are scaled accordingly.
- Most villagers or townsmen don't deal in cash. They will accept coins from wandering heroes, but by necessity it will be at greatly inflated prices. If a night in the flea-bitten inn costs 1 *cp*, the innkeeper can throw in a couple of pints of ale and still make a profit.