Don't trust my scale

I agree with Dennis. I find that to be really accurate, I need to close the plastic lid on my scale so that my breathing and other moving air doesn't fluctuate the readings. The scales measure pretty small increments and grouping the pellets in .1 grain sizes helps eliminate much of the error. I haven't seen an impact difference between even .2 grain differences, though.
 
When weighing in the 100th of a grain (.01), without a clean room, you can expect differences. Like you said, not much, but there will be differences. Drives me nuts to re-weigh and get different weights, but it's the name of the game. Gave up re-weighing - ever. Just too many minor changes in weight. So long as it's within a 10th of a grain, who cares?

I use the $10 eBay diamond scale and it seems to do well, Still gives me different weights on different times weighing.

Consider that humidity, air movement (fans), oil from your fingers, dust, etc will effect weight.