Have you thought of a way to consolidate transactions? When trying go through, correct, and mark the data, one often has to scroll through the multiple order executions sometimes within the same second. Ideally, you would consolidate by day using average time with a little ‘+’ mark to expand the actual separate transactions for editing.
Permanent consolidation would be another solution where the low level transactions get permanently removed. In that solution, a separate database could maintain the low level transactions with links pointing there and possibly reversibility. This would make the recompute process a little faster, but my other suggestion on optimizing recomputes would obviate this need. I suspect the first alternative is more consistent with your existing model.