Sounds like you may want to look into creating your own calculated fields that would contain the aggregated totals.
Edit: Like in my comment to the other answer: create a different dataset which will aggregate the data in the manner you want. Unless you are dealing with monstrous rows returned, this should not be much of a performance issue, and in the long run it's probably a lot better than trying to hack together a solution off of a dataset which may not be suitable.