In your cs cart root directory look for the following code in config.local.php :
// Tweaks
/*
$config['tweaks'] = array (
'js_compression' => false, // enables compession to reduce size of javascript files
'check_templates' => true, // disables templates checking to improve template engine speed
'inline_compilation' => true, // compiles nested templates in one file
'anti_csrf' => false, // protect forms from CSRF attacks
'disable_block_cache' => false, // used to disable block cache
'join_css' => false, // is used to unite css files into one file
'allow_php_in_templates' => false, // Allow to use {php} tags in templates
'disable_localizations' => true, // Disable Localizations functionality
'disable_google_base' => true, //Disable obsolete google base functionality
);
If join_css is true, then your css files are probably minified and compressed into a that /var/cache/templates/css folder.