|Although I am not familiar with the term "countback", this technique will eliminate ties:|
e.g. With your scores in C1:C10, enter this in E1 and drag it down:
=C1 + ROW() * .0000001
This will increase the values in Column C by a small multiple of the Row in which the score resides. The more zeros you use, the smaller the difference. This could make a difference depending on the precision of your scores.
Granted, the problem with this method is that the further down the column a given score is, the higher the rank. For example, if your names are in alphabetical order, Joe A's score of 50.6 will always be less than Joe Z's score of 50.6 since the Row number for Joe Z will be higher.
You could include the RAND function in there someplace to make the increase more random, but there is no guarantee that RAND won't return a duplicate number at some point. Chances are slim, but it could happen.