Amazon offers the Tom's of Maine 5.5-oz. Antiplaque and Whitening Toothpaste 2-Pack in Peppermint (pictured) for $6.38. Add it to your cart via Subscribe & Save and it falls to $6.06. With free shipping, that's $3.03 per tube and roughly $2 below what you'd pay at your local Walmart; however, we saw it for a buck less in September. This toothpaste is fluoride-free.
Also available is the Tom's of Maine 4.2-oz. Children's Toothpaste 3-Pack in Wild Strawberry for $7.44 with free shipping via Subscribe & Save. That's $2.48 per tube and $6 under what you'd pay for this quantity at your nearest Walgreen's. (We saw a 2-pack for a dollar shipped in July.)
Be sure to cancel Subscribe & Save once your order ships to avoid being billed for subsequent shipments.