Depending on how you add the Total rule, you have different options in the Add Total rule.
If you would use the Add Total rule from the icon’s menu, below the Ruleset then you would get the options to check/uncheck Cumulative Total and Grand Total:
However, when you are first selecting the columns you want to group the totals (hold Ctrl) then you do not get the options for check/uncheck Cumulative Total and Grand total:
These windows should be consistent. Also, when you first select the columns, you will need to Edit the rule to be able to uncheck the Grand Total as this is flagged by default (but hardly ever used). So you will need to do an additional step.
Consistent dialog for the "Total" function
The enhancement request has been accepted for implementation in future releases.