Of course you can. You just need to be smart about it.
We just renovated our bathroom by putting tile over our builder-installed unit, put in bullnose along the sides for custom built-in look, and tiled the floor. We chose tile from a box store. When we went to pick it up, the guy came out with our boxes of tile with one box completely broken. Still, he brought it to us carefully balancing it in his arms to not lose any of the broken pieces. Really? Of course we could not take that box! He then suggested we take the rest of the boxes and he would order one more. NO again! You must always get the same dye lot of tile or you will see the difference as it is installed. He reordered the entire order, and we were able to put that tile in our bathroom. So you must be very diligent when working with box stores. Know what you are doing, and you can save a little bit of money. We chose to use them this time because we thought the tile was just the color we wanted. There is far less selection than in a tile store but sometimes you will find what you love. Then go for it. Also always use porcelain tile and not ceramic tile. Ceramic is cheaper but is made of clay… it chips and cracks and when it does you will have a dark clay spot forever in your floor. Porcelain is hard and durable and will last for years. When you select your tile, find what you are willing to live with for a long time, because it will last!