Hi Greg,
I'm a strong advocate for transparency on grades. Some subjective "wiggle room" is a common request, but I personally believe that it needs to be fair and explainable. If one student receives 89.7 and earns an A- while another with the same percentage earns a B+, it's difficult to justify that. It's easy to adjust the Letters breakdown so both get an A-, but if an instructor really wants to give different grades, I advise them to use a participation grade to force a differentiation. While some might suggest using extra credit, I don't believe that it is really additional work they did, but rather, a measure of effort, which I classify as participation.
My two cents.
-Mark