Any best practices on handling Rejected Purchase Orders? Some people don't want to see them, but from my research we can't close them in a rejected state. I also don't like the idea of deleting the Purchase Orders either.

Leave them in rejected state if you don't want to edit and use these again. You can also use lock record action in workflow to remove edit option from these.

The downside is keeping them in rejected states make them still populate in the user view. The user still may want to edit the rejected PO and make the changes to get it approved.

Use lock record action after approval