If you have all 10’s but only one 9, it doesn’t matter how many more 10’s you get, your average will never come out to 100% although it may only be a thousandth of a point from it…. You could be at 99.9999999% and it will only ever show you at a 9. That’s what I think.
With this sort of math in mind...i had my first two occasions to deal with the "we don't need pennies anymore" rules. The first my bill ended in 0.38. They charged me 40 cents. The second one my bill ended in 0.52 and they charged me the two cent difference. I wanted my two cents from the first encounter to be covered by a nickle change in the second. Math is supposed to be a known quanitity. As we can see the math as used is at the discretion of someone else, not us.