I agree with this. To me, our choices are:

* Store everything as an integer mg/dL (I still think we should round, because 59.9999 is 60, but I suppose in a world where accuracy of 15% is considered good, a value off by 1% is immaterial).
* Store everything as a float mmol/L and deal with conversion to int only on output.

I was personally biased toward the floats but I don't think it matters very much. In either case, I think we ease the "omg you're converting my values!" worries by storing the text string with the original value, whatever it may be.