This very interesting article shows without small coinage trade grinds to a halt. It shows small coins are valuable to keep the economy moving and make trades fair to both parties. Another reason copper cents have value.
Abstract of: Redish, A., & Weber, W. E. (2011). Coin sizes and payments in commodity money systems. Macroeconomic Dynamics, 15(S1), 62-82. doi:10.1017/S1365100510000593
After the fall of the Roman Empire most of the European Kingdoms devolved into a commodity monetary system based solely on silver coinages limited to a single size. This made trade very difficult. For example England used a silver penny weighing of 2.3 grams. This single coin was valued as a day’s wage for unskilled labor. But the coin was too large to make purchases for example, the bread buyer would be required to buy four loaves of bread for the only available coin. This single type and size of coin prevented haggling and turned the economy into a take-it-or-leave-it (TIOLI). Traders without ability to make minor adjustments were unable to achieve fair prices. This lead to persons more ignorant be taken more frequently by those more proficient.
In Commodity Money Systems small change is the lubricant to keep the economy moving.