Tubhumper,
There is no significance to the number of decimals after a basic dimension as per ASME Y14.5M-1994. The feature you are dimensioning is controlled by the geometric tolerances you have applied.
The standard states that you do not show the trailing zeros on metric dimensions. I would assume that this is done to make metric drawings look different from English units. I wish my CAD software sould support this properly.
If the dimension is not basic, ASME Y14.5M-1994 allows a tolerance note to define tolerances as per the number of decimals.