I have a spread sheet setup to markup list price of ~2500 items and display the result in column D

This the formula I have in column D It works fine, my question is what would I need to add to this function to display a minimum of 6.00
=(LOOKUP(ROUNDUP($E2,0),$R$2:$S$12,$S$2:$S$12))*$E2

file attachment here doesn't seem to be working, I uploaded it to my server
http://thegallery.us/temp/markup.xlsx
I trimmed it down to 276 just to reduce the size for this post.

Thanks for any help with this!!