add a class to style groups of tables

Using Responsive Theme by cyberchimps. How can I apply a class to a group of tables? I use your plugin to create a lot of tables many of which are the same structurally just different content in the cells, row and column headers are the same. To hide columns at different viewports I would have to enter css for each table several times for each @media. Isn’t there a way to create a table class like “mytable” which could then be styled one time and called with the short code on the page.
For example:
table.mytable .tablepress .column-3 {
display: none;
}

and then on the page have something like this
<table class=”mytable”>[table id=”100″ /]</table>

Can’t seem to get anything to work using this concept. Responsive theme already has a .table class so I don’t know if that’s the problem or not. If I can’t apply a class then I would have to add styling for each @media size for each table which would be extensive. Thanks in advance for your help.

http://wordpress.org/extend/plugins/tablepress/