Drupal Commerce hide cart to non authenticated users
A quick fix might be to write a tiny custom module that overrides the access callback for the cart page:

function MYMODULE_menu_alter(&amp;$items) {
  $items['cart']['access callback'] = 'MYMODULE_cart_access';
}

function MYMODULE_cart_access() {
  if (user_is_logged_in()) {
    return user_access('access content');
  }

  return FALSE;
}