Sketchup’s accuracy never changes, only the display precision. It can display to 6 decimal places of a mm if you want.
How you set the display precision is up to you and how you are working.
Too course and it will round up and not show accurate dimensions, too fine and you have too many decimals to deal with.
With inches for example, if you have the display precision set to 0" it will only show whole inches, but as you increase the precision it will show more accurate dimensions.