There is no support in the grid to handle this, so you would have to implement it yourself. There are several ways to try to do it. You could derive your own textbox cell control, and handle the static drawing by swapping out the tabs for spaces for you draw the string.
Or if this is sufficient, a simpler technique would be to handle PrepareViewStyleInfo and swap out the tabs there.
private void gridControl1_PrepareViewStyleInfo(object sender, GridPrepareViewStyleInfoEventArgs e)
{
GridCurrentCell cc = this.gridControl1.CurrentCell;
if(cc.RowIndex != e.RowIndex || cc.ColIndex != e.ColIndex
|| !cc.IsEditing)
{
string s = e.Style.Text;
s = s.Replace("\t", " ");
e.Style.Text = s;
}
}