I tried my hand at Walgreens

So I'm always reading how well other people do couponing at Walgreens.  (Register Rewards are the way to go there.  So adding this new tool in my arsenal has proven tricky.)
Here are a little bit about register rewards.  Walgreens offers them when you buy participating items.  They print after you pay your total and are given to you to put towards your next Walgreens shopping experience.  They DO have expiration dates so this isn't for you if you don't have a Walgreens close.  When redeeming your register rewards (and this is the part I've only heard about, not experienced yet), it counts as a coupon, so if you are already buying five items and have a coupon for each item then you have to purchase a sixth (think something very inexpensive) to be able to use your register rewards. 
So here's how I did at Walgreens (I'll tell you and then tell you how I messed up and could have made my deal much better, I'm still learning, remember):
I bought:
1 Dove Shampoo on sale for $4.00 and I had $1.50 coupon
1 Dove Conditioner on sale for $4.00 and I had a $1.25 coupon
1 Package of Huggies Little Swimmers, on sale for 6.99 and I had a $3 off coupon (good deal!)

Now, the register rewards come in like this.  You are supposed to get $4 of register rewards for each shampoo or condition purchased.  Well, I'm not sure if this is limited to one per transaction or what... but I only got $4.00 in register rewards.  Had I split my transaction into two, I probably would have received that extra $4.  Boooo!  But I can't complain too much.  I got a big thing of shampoo, a big thing of conditioner, and little swimmers diapers for $6.15 including my register rewards.  Not too bad.