Hi Michael,
Thanks for your update.
With 'CurrencyCell' celltype in gridgroupingcontrol, it is not possible to display empty cellvalue. If you would like to achieve this along with the currencycell feature, you can handle the TableControlDrawCellDisplayText event and TableControlCurrentCellKeyDown event in such a way giving functionality similar to CurrencyCell celltype. Here is a minimal sample for your reference in which this has been implemented.
http://files.syncfusion.com/support/samples/Grid.Windows/7.3.0.20/F90488.zipRegards,
Rajadurai