No, sealing the grout on floor tiles is costly and ineffective. My doctor, who I do all types of cleaning for, asked me to seal his grout after it was cleaned. I told him it doesn't work. This man is extremely meticulous about his home. He did all the custom trim and crown mouldings in his house himself. The doctor asked if he could purchase a good floor sealer from me and do it himself. I got him the sealer, at my cost, and he spent the next 2 days sealing his kitchen floor grout. He has a very large kitchen and after those 2 days, was only half done and gave up. 1 year later we cleaned all of his kitchen ceramic tile and grout and there was no difference and there was no difference in the sealed or unsealed side. Both were equally soiled before cleaning, and equally clean after our cleaning process.
When a kitchen backsplash is being installed, there is a grout where the sealer is actually chemically a part of the grout. This way the sealer is all the way through the grout and not only on top. In this case the sealant is highly effective and strongly advised. On certain types of tile on walls or backsplashes, the tile is very porous and everything gets embedded in the tile. Sometimes, even cleaning won't remove it. In these cases, there is a special sealer meant for this use. It too is very effective. Ask your retailer what you need. If they don't seem to have the answers you need, go somewhere else.