I setup inventory items using categories. But I can't find a way to show inventory values with category totals. Is there a way to get inventory values to subtotal by category?

I setup a retail jewellery store with the following inventory categories and items:

1. Earrings
   1. diamond earrings
   2. gold earrings
   3. silver earrings
2. Watches
   
   1. Seiko men's watch
   2. Seiko ladies watch
   3. Swatch watch
3. Rings
   
   1. 10k men's ring
   2. 14k men's ring
   3. 18k women's ring

Now I want the inventory summary report to give me subtotals for each of the categories. But the report just lists the individual items and value of each item. I can't find a way to get the report to give me sub totals for each category.

Any suggestions?