In this example we changed the price attribute and rounded the price with the round() function.

roundprice.php

<?php

// Round the price 
function round_price( $data, $feed_id, $product_id ) {
   
   // round price.
   $round_price = round($data['price'], 2);

   // Store the rounded price in the feed price element.
   $data['price'] = $round_price;

   // Always return data!
   return $data;
}

add_filter( 'wppfm_feed_item_value', 'round_price', 10, 3 );