The goal of each group would be different. By looking at the year distributions, one group could try to establish at what rate pennies fall out of circulation. Their results would be more accurate if they research and find how many pennies were minted each year. By looking at mass distributions, a second group could work on the problem of what metal went into 1943 pennies. A third group could establish some guidelines for choosing a bin width.
Many thin bins can make a set of data look jagged.
On the other hand, thick bins can conceal some of the interesting bumps in data. It will not be a mathematically precise formula, just a rule of thumb that make a smooth histogram likely on the first try. First, the student can load the penny data into the text area. Then the program reads the data to make a control panel. Then the student can adjust the control panel to make a graph.