Cutting 1mg tablets is reasonably accurate. On the odd occasion that one half crumbles or is obviously smaller, I toss them in the bin. Doesn't happen often.

I used a pill cutter with no expectation of total accuracy, nor did that ever feel important (no noticeable physical difference day to day). The 5mg pills could be split into 8 parts, the smaller 1mg into 4 parts. The pill was placed in the V of the cutter. When dealing with segments, I did one at a time, adjusting each with something small like a metal toothpick until it seemed centered.

I only cut one pill of each type at a time, using up the pieces before cutting another. Toward the end there were six old pill containers with labels like 1/8-5mg and 1/2-1mg (blue ink for 5mg bits, red for 1mg bits, really didn't want to confuse them.) Between the cutting and the math, it was a bit fiddly, but worked for me.