1. A system for performing targeted marketing on customers in a retail establishment comprising: apparatus for entering selected indicia from instruments presented by customers at a point-of-sale, in order to generate a unique identification code for each customer; a bar code reader for detecting the universal product code on products purchased by said customers; a terminal at the point-of-sale for entering data relating to the customer's shopping transactions; a processor responsive to said apparatus, bar code reader, and terminal for creating a centralized database of the store's customers' transaction data during previous customer visits and data relating to universal product codes of products previously purchased by said customers, in association with said customers' unique identification code; said processor generating a signal upon entry of unique identification codes of customers whose transactions prior to the current shopping visit at the store meet one of a plurality of predetermined purchasing history criteria; and circuitry responsive to said processor and said database for dispensing a sales promotion at the point-of-sale to said customers whose prior transactions meet one of said predetermined purchasing history criteria, wherein said sales promotion provides different incentives to customers having different prior purchasing histories, such that said customers are incented to return to the retail establishment to purchase products in a future transaction.