The age old question of; to tap or not to tap...

If your measure has a cut funnel I suggest overfill it slightly, and then cut the charge level. I have weighed out charges to see how different they are, and it would surprise most as how close a loose pour cut charge is. If it has no cut funnel, I have taken a patch knife and struck off/dragged the measure level like your mother did with spices in the kitchen when baking.

If you are one of them that thinks by tapping you can get more powder into the measure, instead, try setting a slightly heavier charge on your measure, and pour a loose cut charge instead without tapping. If you must tap, then try to tap the same number of times in the same way each and every time.

Actually a grain or two will not make a huge difference in your accuracy. Some rifles I have, can shoot the same with as much as five grains difference. What you're doing is trying to develop a pattern of loading so that every time you load you do it the same as the time before. This conformity in loading will lead to better accuracy in the long run.