wp-travel-child_customize

function wp_travel_child_customize_currency_symbol( $currency_symbols ) {

  if ( is_array( $currency_symbols ) ) {

     foreach ( $currency_symbols as $code => $text ) {

        if ( 'USD' == $code ) {

          $currency_symbols[$code] = 'USD$';
        }

     }

  }
    
  return $currency_symbols;
}

add_filter('wp_travel_currency_symbols','wp_travel_child_customize_currency_symbol');