The board shall, pursuant to regulations prescribed by it, refund or credit to a distributor the tax imposed on tobacco products pursuant to Article 2 (commencing with Section 30121) and Article 3 (commencing with Section 30131) of Chapter 2 that is paid on the distribution of tobacco products that were returned by a customer, when the distributor refunds the entire amount the customer paid for the tobacco products either in cash or credit. For purposes of this section, refund or credit of the entire amount shall be deemed to be given when the purchase price,

less rehandling and restocking costs, is refunded or credited to the customer. The amount withheld for rehandling and restocking costs may be a percentage of the sales price determined by the average cost of rehandling and restocking returned merchandise during the previous accounting cycle.