We rounded properly for percentage to absolute value, but we always floored the other way around.

The new code achieves this by always rounding. This way the following rule holds (assuming the the min value is 0 for this discussion)
  x = round (round (x * scale) / scale)
with
  scale = (max - min) / 100
and assuming that scale >= 1

If scale < 1, the rule holds for the other direction.