Answer

1. In Tableau Desktop, add the field you want a running sum for to the view. 
2. Select the drop down arrow > Quick Table Calculation > Running Total to see the full extent of data in the dataset. 
3. Select Analysis > Create Calculated Field to create a calculated field.
4. In the Calculated Field dialog box that opens, type a name for the field.
5. In the formula field, create a calculated field similar to the following and then click OK:
   IF NOT ISNULL(SUM([<Field>])) 
THEN RUNNING_SUM(SUM([<Field>]))
END
   where <Field> is the field that is used in the running total quick table calculation.
6. Create similar calculations for all measures in the view that are being calculated as running totals.
7. Replace the running total quick table calculations in the view with the newly created calculated fields.

Additional Information