Does anyone know how to rearrange the Shopping Cart sidebox so that when I buy my products they will be separated into their subcategories in the sidebox? I see the php file under sideboxes, but I'm not sure how to write the code to group them by category id.

example: I sell cabinets so I want in my shopping cart sidebox for all the base cabinets to be grouped together and all the wall cabinets to be grouped together even if the customer buys a base, then wall, then 2 walls, then 3 bases. I want them to be grouped by their ID.