Here’s an unadvertised RR promo at Walgreens:
Buy 4 boxes of Fiber One Chewy Bars, on sale for $2.49 each
Use 4 $0.40/1 coupons found here and here
Get a $2.50 RR
Final cost: $1.47 per box
I am not sure how many boxes you have to purchase to get the $2.50 Register Reward. If you can actually purchase less than 4 boxes, this deal will become even better! Also, there may be more participating products included in the Register Reward promotion.