Don't get too hung up on precision, SR's are just there to simplify the order of things.
The way I do it is: ask for everybody's statement of intent, I respond with a 'okay you go on 4' or 'you cast Bladesharp on 3 then strike on 8'. Once everyone has their slot I count up from 1-12 and the players jump in accordingly, sometime's as lordabdul said, stuff only happens at certain SR's, this doesn't mean there is a perceivable gap