I would straighten as best as you can. The fabric may be reasonably straight off the bolt and then it might not be. I have had some really crooked fabric. But as suggested. I would only cut the squares from one end and not straighten the entire length. This would be a more economical use of the fabric especially if it is very off grain. Cjecl the end of the strip to see how much off/on grain it is and if you will have enough to get the straight 10" cut.
I think I am rattling here but hope you can understand what I am saying.