Reloading: Working up a load, how small to measure the powder increments?

I'm working up a load for my .30-06 using Sierra 180g GameKings, Rem brass, CCI primers and IMR4350.

My initial 5 shot loadings were 53gr, 54gr, 55gr and 56gr. Best group out of those was at 55gr and roughly MOA.

So, I was planning on loading another round of testers at 54.5gr, 55gr and 55.5gr to see if there is any improvement in accuracy between the full grain differences. Is that the best way to do it? Or should I load in smaller increments like 54.6, 54.8, 55, 55.2, 55.4?

I'm not really sure how much a fraction of a grain of powder will affect velocity and noticeable accuracy. A full grain on either side of 55gr increases the spread 3-4x (attached pics).

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Reloading: Working up a load, how small to measure the powder increments?