The quantity pricebreak table defines the start quantity for when a discount should be applied and the matching discount percentage. Any quantity can be added with any percentage value and it will sort and calculate shopping cart and order total accordingly.
Each category can be selected to apply the quantity pricebreaks from the pricebreak table. It would be easy to add multiple pricebreak calculations if that becomes necessary one day. The right column shows the highlighted category, with the last entry showing if a pricebreal should be applied or not.
By adding products to the cart, the header cart info keeps the customer informed about the amount of items in his cart and the volume discount that will be used for the calculation. Cart and order total calculations automatically adjust with each item added.