Amazon offers the Rachael Ray Nutrish Natural Dry Dog Food 5.5-lb. Bag for $4.79. Order via Subscribe & Save to drop the price to $4.55 and net free shipping. (Walmart charges a few cents more.) That's the lowest price we could find by $4.
Be sure to cancel Subscribe & Save after your order ships to avoid being billed for subsequent shipments.
Update: It's no longer available at Amazon; however, Walmart offers it for $5.28 with in-store pickup.