AnswerBelow is an example of displaying the cumulative sales values for each category in a subtotal.
1. Create a calculated field and name it Cumulative Sales.
IF SIZE() > 1 THEN RUNNING_SUM(SUM([Sales]))
2. Add Category to Rows.
3. Add Sub-Category to Rows.
4. Add Measure Names to Filters and only select Sales and Cumulative Sales.
5. Add Measure Names to Columns.
6. Add Measure Values to Text.
7. Right-click Cumulative Sales in Measure Values Shelf and select Edit Table Calculation. Set it as follows: