Any discounts you offer in your newsagency should be managed by your newsagency software. I see too many staff in newsagencies applying discounts manually. This leads to mistakes that cost either the customer or the business owner. Good software handles all sorts of discounts including catalogue sales, volume based pricing in a single purchase, volume based pricing over several shopping visits, VIP shopper discounts, local community group member discounts, end of line discounts and more.
The image I have included shows the automated handling of the Hallmark BUY 3 FOR $10 card offer. The cards are $4.99 each but if a shopper purchases three at once they are discounted to a total of $10. Handling this automatically through the software sales time and cuts mistakes at the counter.