When we put an addition on our house upteen years ago I wanted ceramic tile on our kitchen floor. Went to the tile store and picked out what I wanted. Man there said trick with keeping grout clean was to seal with 6 - yes, 6 - coats of sealer. Thankfully that stuff dries really quickly. I spent 2 days sliding around on the floor with a little paint brush putting on that sealer. But, the grout on my kitchen floor cleans up like a charm. When the tile guy installed the wall tiles in our bathroom, he wasn't quite as diligent - plus the grout lines were much thinner. They get a little scummy. I usually use SoftScrub on my bathroom tile and it seems to work quite well.