One can, many do, and some talk about doing it. It's a "season to taste" approach.
For me, the amount of additional brewing salts varies based on the brand of DME. Brewing Engineering has a couple of pages that provide some brand specific information. How to Brew, 4e, chapter 8 also some general information.
Over the past year, a couple of us have talked about "adding minerals in the glass" in a controlled manner, then using that information to "dial in" the brewing salt additions in the next batch. "State of the art" for this technique appears to be using three 4 oz pours - one for CaCl additions, one for CaSO4 additions, and one as a 'control'. I'm finding that one doesn't need to do this for every recipe - just cover the broad style groups ("Pale Hoppy", "Amber Malty", ...) for each brand of DME/LME.
edited for formatting.