I have not yet done this myself, but the Glade scented oil candles that are on sale BOGO the week of January 13 will reportedly produce Register Rewards. Since the candles may be bought free using the coupons mentioned in this post, you could make some money on it. It's not a huge amount, but the reported Register Rewards are as follows:
Buy 3, get $2 RR
Buy 4, get $3 RR
Buy 5+, get $4 RR
Note: While you may not technically be paying for any of the Glade, it still counts as a "purchase" toward the RR.
Edit: My information about this deal was incomplete. It's the Glade scented oil plug-ins that are producing the RR, not the candles. No free RRs this time around...