It is now possible to set up Retail Promotions for use in the "Point of Sale" and "Invoicing and Customer Orders" options.
Retail Promotions are a special kind of discount that are available for a limited time period and act on multiple items bought by the customer (Buy one - Get one free, Mealdeals, Buy three get cheapest one at set price etc).
- See How do I set up Retail Promotions? for more details.