NinjaBrew allows you to setup different sales promotions and discounts. There are three types of sales events. The main one being scoped sales events. These are sales between a certain date range. They either apply to a certain product group, or to sales of products belonging to a specific supplier.
There are two types of broad sales events. The first one is a global discount that applies to the total invoice. The discount is calculated on the sub-total before taxes are applied. The second sales event in this category applies to obsolete items. Both these sales events can be activated or deactivated at will and apply to the pre-tax sub-total.