All I can say is our template handles the display of prices identically to the std VM layout -
you can prove this by completely disabling Puremart
To do this just rename the folder

ROOT/templates/YOUR_TEMPLATE/html/com_virtuemart

to

ROOT/templates/YOUR_TEMPLATE/html/com_virtuemart2

if your using over-rides set them off as well in Configuration->Templates


I'm as confused by VM's silly meaningless price labelling as the next guy - please just experiment with or perhaps ask on the VM forums for exactly what you want..

Cheers

I'm sorry - I don't know - this is the wrong forum.. we gladly support our templates but if this is as you say a calculation error within VM then you should ask on the VM forums...