actually there is a good way.
if u got the cash, dun pay cash. pay by credit card. then pay in full next day to the credit card hahah... can earn points!
i just bought 35mm yesterday and pay in full using my premier miles card... then get the miles point already, today will go and make full payment to the credit card. the drawback is... u pay extra charge for cc payment. but worth it! that few XX dollars for that miles points.