In games copper generally takes the place of pennies and 100 of them will make a silver coin. What were the actual conversion rates and how much was a copper coin worth?

I'm looking at 4th/5th century CE Rome. At this time the basic coin was called the nummus. It was a bronze coin rather than a copper coin. It was officially worth 1/7200 of a solidus (a gold coin of about 4.5g weight) but merchants more commonly valued it as 1/6000 of a solidus. There were 4 nummi to a follis, which was a bronze coin with a little silver coating. And 250 nummi to a siliqua, which was the main silver coin and worth 1/24 of a solidus.

In terms of what you could get for these coins, you could buy enough wool to make a cheap cloak for yourself with 1200 nummi/4.8 siliquae or you could buy a cheap woven cloak for 2000 nummi/8 siliquae. 24 nummi would buy a pound of meat. One modius of grain (8.73 l) was worth 180 nummus, and this was the daily wage of a cavalryman.