Yeah scanning the receipts takes the longest time in the whole process. So you should make sure that you have a fast and simple scanner. I can recommend to buy a simple photo scanner like I did. It's just a couple bucks and it will save you so much time. And the quality was near perfect. Even very old receipts could be parsed after scanning with it.

When it comes to rotation, you can try http://www.fmwconcepts.com/imagemagick/textcleaner/. It will rotate your scan if it's not perfectly aligned.