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-gp 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.

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.