Yeah, but the slight variance is still smaller than compared to when a pump stops filling at full tank, or when the fuel light comes on each car, or the driving style of each individual.
Assume you lose 10 times the amount that I claim, so 100ml. When petrol hits $2.00 per litre, that means you are losing 20 cents per fill up. That's less than if you decide to fill your tank at a petrol station advertised at $2.00 per litre instead of $1.99 per litre.

