http://www.bestbuy.com/site/promo/save-on-gaming-cards-20160723
Best Buy has Steam (and all other gaming currency cards they carry) for 5% off. Just a bit more to stack with the 15% bonus G sale. Sale ends 10 PM PDT and 2 Day shipping is free. You won't receive the cards in time for the bonus G sale if you opt to have it shipped but you can always hang on to them until the next one rolls around.