You round to the nearest value that you have on your scope. In your case I would adjust my scope to 6.25 MOA. At 500 yards your error would be .52" high. At 1000 yards the difference would be a little over an inch. For all but the most stringent accuracy requirements this is pretty close. Some programs will allow programming of the clicks required which will round to the nearest click. This can be burdensome at the longer ranges, with it being easier to just do a mental calculation. If a greater degree of accuracy was required you could make the adjustment with your reticle, calculating the difference, or use a scope with finer adjustments, ie. 1/8 MOA click values.