Staples offers the Charmin Basic Toilet Paper Double Roll 20-Pack for $10.99 (55 cents/roll). Plus, Staples Rewards members receive free shipping. (Not a member? It's free to join.) Excluding the below mention, that's the lowest total price we could find for the quantity by $4, although we saw a 24-pack for $9.99 (42 cents/roll) in July. Each 1-ply roll includes 264 sheets.
Don't mind going to the store? For in-store pickup only, Kmart offers the 20-pack to Shop Your Way Rewards members for $12.39.