commerce_discount_set_price_component() should also round the discounted amount

Currently commerce_discount_add_price_component does the following:

  // Calculate the updated amount and create a price array representing the
  // difference between it and the current amount.
  $discount_amount['amount'] = commerce_round(COMMERCE_ROUND_HALF_UP, $discount_amount['amount']);

But commerce_discount_set_price_component() doesn't.