[Australia Post] If you need to adjust tax rate, you can add the following snippet.
add_filter( 'woocommerce_shipping_australia_post_tax_rate' , 'woocommerce_shipping_australia_post_custom_tax_rate' );
/**
* Adjust tax rate
*
* @access public
* @since 1.0
* @return void
*/
function woocommerce_shipping_australia_post_custom_tax_rate() {
return '0.09090909';
}