The flour(s) you would normally use to make bread appear to only come in increments of 5, 25, and 50 pound bags. I tried and couldn't find any regional mills that sold 10-lb increments, either.
Sam's Club sells All-Purpose and Bread flours in 25-lb bags, those are also the only ones I could find that King Arthur
sells in that size bag.
Don't know where you live, smag - but sometimes if you can't find a 25-lb bag of flour on your store's shelves - they might be able to order it if it is something that is available from their regional distribution center. But, compare the price of a 25-lb bag to 5 5-lb bags. The 25-lb bag of King Arthur bread flour is actually a few cents more than 5 5-lb bags on their website - and the 25-lb bag from Sam's was about half the KA price.
Of course, if you want to move up to the flours that professional bakers use - you're back to looking at 50-lb bags.