public function tax()
{
if (isset($this->amount->tax)) {
return $this->amount->tax;
} elseif (isset($this->order->shipping)) {
$tax = new Tax($this->order->shipping->country, $this->order->shipping->state, $this->order->basket);
$this->amount->tax = $tax->amount();
return $this->amount->tax;
} else {
return 0;
}
}