public static function _insert_tax_rate( $tax_rate ) {
		global $wpdb;

		$wpdb->insert( $wpdb->prefix . 'woocommerce_tax_rates', self::prepare_tax_rate( $tax_rate ) );

		$tax_rate_id = $wpdb->insert_id;

		WC_Cache_Helper::invalidate_cache_group( 'taxes' );

		do_action( 'woocommerce_tax_rate_added', $tax_rate_id, $tax_rate );

		return $tax_rate_id;
	}