In your POS software
Go to Sales-Register > Dissection Companion Sales by Period.
Besides telling you sales totals for a department, it can tell you so much more.
Try looking for is an abnormally high number of products for other stuff that sells well with that department. It is beneficial as it can help you select a product to display near a department prominently. This is a well-known method of increasing incremental sales that all majors use.
What you do is take an item that sells well with that department and place it in that department's area. There is nothing wrong with a good seller having a few spots in the shop.
As you can see here (green arrow), there are quite a few extra sales that could be made by moving some other companies' chocolates close to Darrel Lea Chocolates. Darrel Lea may not like it but ....
Another great use is more long-term. If grouped by department, you can get a feel of where you should position the display for the department. As you can see here by the green arrow, the books should be close to the stationery.
You may be able to pick up a few extra sales if people looking at your book can see your stationery too.
Why not try it now?
Look at a few departments and see if you can get a few ideas. It will only take a few minutes tops.