Add tax on cart total depending on category

woo_functions.php

function woocommerce_custom_tax() {
  global $woocommerce;

	if ( is_admin() && ! defined( 'DOING_AJAX' ) )
		return;

	$flowers_in_cart = false;

	foreach ( WC()->cart->get_cart() as $cart_item_key => $cart_item ) {
	    //check if there's a product under flowers category
	    if ( has_term( 'flowers', 'product_cat', $cart_item['product_id'] )) {
	        $urns_in_cart = true;
	    }
	}

	if($flowers_in_cart == true){
		$woocommerce->cart->add_fee( 'Service Fee', 9.95);
	}
}
add_action( 'woocommerce_cart_calculate_fees','woocommerce_custom_tax' );