Ok, its not the scale. After checking everything recommended I just decided to try weighing a 135 grain et and an empty piece of brass several times in a row. Each time the scale went back to zero properly. Here are the measurements I got :
135 gr Nosler HP - 133.8 (3 times in a row)
Brass - 68.5 (3 times in a row)
I alternated measuring the bullet once then the brass then the bullet etc. Each time the scale went back to zero.
I was concerned that a 135 gr bullet would measure 1.2 off, then I noticed a rubber band half hanging from the 10's place weight. So I took it off and the bullet then weighed in at a hair below 135.
Then, satisfied with the scale itself I turned my attention to the powder dispenser. It's a Lee Auto Measure and it weighed the 5.4 gr powder charges as follows:
5.2, 5.1, 5.2, 5.1 (3x). Is my powder dispenser that off? I'm using the minimum charge for a Nosler 135 with Bullseye powder. I could also move up the charge to 5.7 which would be within a safe margin of error (max load is 6.4). But I'm still concerned that the powder measure would be .3 gr off. Should I be?