Se intendi il totale dei totali :



$totali=0;
while ($rw=mysql_fetch_array($rs))
{
echo "<td width=10% style=padding-left:10px>".$rw["id_prod"]."</td>";
echo "<td width=40% style=padding-left:10px>".$rw["prodotto"]."</td>";
echo "<td width=10% style=padding-left:10px>".$rw["pezzi"]."</td>";
echo "<td width=20% style=padding-left:10px>".$rw["prezzo"]."</td>";
$totale = number_format($rw["prezzo"] * $rw["pezzi"],2);
echo "<td width=20% style=padding-left:10px>";
echo $totale;
echo "&euro;</td>";
echo "</tr>";
$totali+=$totale;
}

echo "<tr><td width=20% style=padding-left:10px>";
echo $totali;
echo "&euro;</td>";
echo "</tr>";
echo "</table>";