I am glad that my local chain store offers to tear wider fabrics. At least I know it is on the straight grain.
I have also had the staff check the cut end to make sure it is straight, before cutting my yardage.
Years ago I bought a woven plaid, no excuse at all for being off grain when you have a line to follow. The cut end of the fabric was 12 inches off. This was at Walmart and the cutter had to come from the shoe department. She was not a sewer, but when I pointed out how off the cut was, she measured from the short edge.