On the "Save before you Shop" option...the same holds true for treasure chests with random items. Save before you open them, and if you don't like what you get, reload! Sometimes some items are "planned" and others are random; in that case, the "planned" item (generally a key or an artifact) will always be there, and the rest of the items will reload. Quite often it's just more of the same, but every so often a "goodie" will pop in!
-Sazerac