In your point of sale software, now is a very powerful tool to see your cash breakup. Any study of this is getting into the heart of a business.
So off we go, in the main menu select "End of day."
Now in your Options menu marked in green, tick everything, so you are going to get as much detail as you can.
Now in the Option above, as for the following
Now you are going to get a detailed report on all the cash takings for the last 12 months.
Now one part that I do suggest that you look at is the Sales Payment Breakup, in that you can see an analysis of how people are paying in your shop. I am sure just that alone will make interesting reading.