The DataGrid does support multi-level grouping of the entire set (using multiple search parameters), but this doesn't sound like what you are looking for.
If I understand your question correctly you want aggregate data to be displayed in a grouped format instead of the whole column sum/avg/min/max.
This is currently not an option. If this is a requirement for you I suggest entering a feature request on MXDN for this.
This feature is available at present?