Comment by Telaneo

The only times I've had splitting bills become a problem are with unreasonably large tables (10+), and at that point, you should be upfront about it before you place any orders, since that fixes the problem.

I assume it's a hard problem to solve if you don't have POS system keeping track though. If all you've got is pen and paper, it's probably better to just split the bill equally, assuming nobody had 6 40 USD cocktails. Or just have someone pay for the whole thing and settle it all in post.