Display WooCommerce prices exlcuding tax for distributors.

plugin.php

<?php
/*
Plugin Name: SunStofey WooCommerce Prices Excluding Tax for Distributors
Plugin URI: https://www.pronamic.eu/
Description: Display WooCommerce prices exlcuding tax for distributors.
Author: Pronamic
Version: 1.0.0
Author URI: https://www.pronamic.eu/
*/

/**
 * Override WooCommerce tax display option for distributors.
 *
 * @see http://stackoverflow.com/questions/29649963/displaying-taxes-in-woocommerce-by-user-role
 * @see https://github.com/woothemes/woocommerce/blob/v2.2.3/includes/admin/settings/class-wc-settings-tax.php#L147-L158
 * @see https://github.com/woothemes/woocommerce/blob/v2.2.3/includes/admin/settings/class-wc-settings-tax.php#L166-L178
 * @see https://github.com/WordPress/WordPress/blob/4.6.1/wp-includes/option.php#L37-L52
 */
function sunstofey_override_woocommerce_tax_display( $value ) {
	if ( current_user_can( 'distributor' ) ) {
		return 'excl';
	}

	return $value;
}

add_filter( 'pre_option_woocommerce_tax_display_shop', 'sunstofey_override_woocommerce_tax_display' );
add_filter( 'pre_option_woocommerce_tax_display_cart', 'sunstofey_override_woocommerce_tax_display' );