以两位小数显示货币，但保留所有可用的小数

Quick(I hope) question. I've got this DataGrid, containing a few currency column's. What I can't seem to find is how to display the currency in 2 decimals. But maintaining a possible 3 or 4 decimal value in the cell. If tried some string-formatting but that actually changes the value. And so does a IValueConverter of course. So what am I missing? or could anybody point me in the right direction?Quick(I hope) question. I've got this DataGrid,