An advertising service divides a consumer transaction at a POS location into multiple time frames. The service then determines an advertisement (ad) for display in one of the time frames and displays the ad in one of the time frames. One of the time frames spans one of the following activities: waiting for a consumer to begin a transaction, greeting a consumer, beginning a transaction, selecting a form of payment, swiping a card for a form of payment, entering a security code for the form of payment, identifying a product for purchase, displaying a total cost for products identified for purchase, signing for a purchase, thanking a consumer his purchase, surveying a consumer, promoting an event, applying for a credit card, informing a consumer, identifying a consumer, interacting with a consumer, and passing through an interstitial period. Determining the ad for display in one of the time frames includes transmitting information about the transaction to an ad-management service that then determines the ad for display based on the transmitted information. A response indicates the determined ad. The service prioritizes multiple ads competing for display and determines the ad with highest priority as the ad for display. The service displays the ad in the one time frame or in a frame following the one time frame. The service advances from the one time frame into another time frame and repeats the determination and display with the other time frame.