Child theme style.css versioning

Are you sure the version is included in style.css in the right way? In that case this should really work (hook with wp_enqueue_scripts):

    $theme_data = wp_get_theme();
    wp_register_style('your-style-handle', get_template_directory_uri() . '/style.css', '', $theme_data['version'], 'all');
    wp_enqueue_style('your-style-handle');

While developing you may not want to change the file version in style.css all the time, in which case you could use filemtime( get_template_directory_uri() . '/style.css' ) in stead of $theme_data['version'] in above code. Codewise that would be the proper thing to do. Otherwise, beware of browser cache issues.