Hi,
Since it's an IIC version with a one byte transfer on poll you have, the range (10..80 cm) will be divided up in 255 steps, but each step is NOT of the same magnitude - the longer the distance, the lower the resolution.
Accuracy, which isn't the same as resolution, determines the repeatability and will have some inter-device tolerance.
I haven't seen any hard data on that gathered on a scale to be statistically significant, but from your wording (accuracy vs. small change), it is unclear what you really wants to know.
Perhaps you could tell what you need, then perhaps we can find you a solution.