Hello. I tried to do same order with VM 2.0.020b and its true that VM does not save discounted price without tax. So invoice looks like this with VM 2.0.20b:
"Tax" is correct but base price is without discount. VM added some more fields to database in next versions. So probably help for you would be to upgrade somehow. Also it is possible that we can mask it somehow for older VM (its final price - tax), but generally it is better for everybody to upgrade to newest VM.
Also I don't know if it will solve all your problems (it will display old prices strikethrough + override prices), maybe you will have some other requests, we can adjust our component for that.