There is no way to "rinse and repeat".
If you were to try and use Rewards to buy something that earns rewards, you would not get any new rewards. In other words: if you tried to buy something that earns 100% rewards and paid using your rewards, then you would earn 0% rewards on the purchase. In other words, you need to use new money to earn rewards (so use your ink card and earn 5%).
This is similar to Staples' policy.
OfficeMax has a different policy. We'll see how long this last given that Office Max and Office Depot are now the same company...