Kmart offers the Glad ForceFlex Drawstring 13-Gallon Tall Kitchen Trash Bag 100-Count Box, model no. CLO70427, for $21.37 plus $8.99 for shipping. Even better, Shop Your Way Rewards members earn around $21 in SYWR points. (Not a member? It's free to join.) Assuming you use the credit, that's about $8 less than you'd pay in local stores. (For further comparison, we saw an 80-count box for $8 via pickup in April.)
Of note, Shop Your Way Rewards members may be eligible for additional credits and discounts.