Agree that it should be fine. I don't think most spokes are supplied in point-millimetre sizes, anyway, so you would be rounding down or up (usually down). The calc should have the end of the spoke at least a millimetre from the head of the nipple, so there is a little bit of scope to play with on this one.

If the spokes have been used before, check any deformation at the elbow and the "mushroom" on the end. Any bends along a spoke should be OK when it's tensioned.