How can I do so that even \"toggle_cart\" is clickable in the same way as \"clickerHeader\" but retains its hover effect (see arrow)?
please see http://jsfiddle.net/real
A minimal change to your existing code is to add the following two lines after the first line of your click function:
if ($elem.hasClass('toggle_cart'))
$elem = $elem.next();
In other words, if the span with the arrow is clicked, pretend that actually the anchor element was clicked. In context:
$(document).on("click", function(e) {
var $elem = $(e.target);
if ($elem.hasClass('toggle_cart'))
$elem = $elem.next();
if ($elem.hasClass('clickerHeader')) {
// etc.
Demo: http://jsfiddle.net/STE48/6/