It is easy to determine your peak hours. It is useful for rostering. But we can do better than that.
The problem is that different departments have different manning problems. Plus their peaks are all different and these peaks often change depending on the time of the year. So what will do here is get their peaks for the relevant period you need.
It takes 10 seconds to get.
Go to cash register reports> Sales - Register> Dissection Sales by Hour
Now put in an appropriate period last year for the period you are trying to get an estimate now. Out will come a report with your shop's sales by analysis of the department sales by time.
It will be worth it to know if you would like to take more control over your employee scheduling