By Anne D'InnocenzioNEW YORK -- Visa ( V), MasterCard ( MA) and major banks agreed to pay retailers at least $6 billion to settle a long-running lawsuit that alleged the card issuers conspired to fix the fees that stores pay to accept credit cards. As part of the settlement, announced late Friday, stores from Rite Aid ( RAD) to Kroger ( KR) will be allowed to charge customers more if they pay using a credit card. The pact, which is being called by lawyers involved in the case the largest antitrust settlement in U.S. history, is seen as a major victory for merchants that have long complained about the billions of dollars in so-called "swipe" or "interchange" fees that they pay to banks for purchases made using plastic. But at a time when shoppers increasingly are using credit and debit cards, merchants will face a dilemma: whether to charge shoppers extra for using plastic, and if so, how to do so without angering them. Marilyn Landis, who was last year's chairman of the National Small Business Association, said that the settlement is a victory for small businesses across the country because it could ultimately lead to banks lowering the fees they charge stores for customers' credit card purchases. Landis, who owns Pittsburgh-based financial services firm Basic Business Concepts, said that would be a big relief. She's now paying 3.75% each time a customer pays with a credit card. If bank card companies reduce the fees they charge her to 2.75%, she would save a dollar on every $100 in sales. "That's huge," she said. According to the National Retail Federation, the nation's largest retail group, swipe fees costs for stores total about $30 billion per year. Mallory Duncan, senior vice president and general counsel for the group, said the settlement is a step in the right direction.