You would need to suppress the quote for that in the shipping module itself for:
/includes/modules/shipping/usps.php
/includes/languages/english/modules/usps.php

evaluate against the $type as to whether or not to build the quote in the:
Code:
          $methods[] = array('id' => $type,
                             'title' => $title,
                             'cost' => ($cost + MODULE_SHIPPING_USPS_HANDLING) * $shipping_num_boxes);