If you are using vb.net you can make use of .Format field to set the $ in the output.
for doing that you need to do the following.
Dim col1 As New DataGridTextBoxColumn
With col1
.MappingName = "<fieldname>"
.HeaderText = "<header>"
.Width = <value>
.Alignment = HorizontalAlignment.Center
.NullText = ""
.TextBox.Enabled = True
.Format = "$00,00"
End With
</value></header></fieldname>
Hope this might help.