Only check roll out as you tire wears if your really anal . A "standard" 700c x 23 on a wheel is 667.5mm diameter (roll out is 2097mm). If you wear off 1.5mm of tread, you're left with a 666mm diameter wheel & tire (roll out is now 2092mm).
A mile is 1,609,344mm, so with a 2097mm roll out wheel & tire, it takes 767.45 revolutions to do a mile. If your tire really has a 2092mm roll out but your computer is set to 2097mm, over that indicated mile you traveled 1,604,795mm, 4.5m short of a mile. 4.5m is 0.28%. Can you live with your computer off one quarter of one percent???

If your running big old knobbies, thats a different story, but why would you be asking in the road forum