For the grid columns, don't specify any alignment, and set it in CSS file.
I am sorry. This does not work. Even if all alignments are unclicked, the html code in the template by default includes for every <th> and <td> a style='text-align:center' statement that cannot be overwritten by the CSS file. CSS in the 'style' statement has higher priority than CSS in the file.
I think 'style' statements set by default should be avoided as much as possible in the generated code as they overwrite any general settings defined on a higher level.