Definitely Kohl's. I got an email back from them awhile ago "congratulating" me on my bonus points.
This is what they put:
Purchase Date Rewards Merchant Rewards Earned
11-24-2011 Kohl's 1606 extra pts
11-24-2011 Pottery Barn 182 extra pts
...considering I only spent $120 at Kohls, I got much more than 5%! No complaining here, though.