Shoutbox

Use a javascript event...

js code:

---

//define this function somewhere
function roundNumber(num, dec) {
    var result = Math.round(num*Math.pow(10,dec))/Math.pow(10,dec);
    return result;
}

// x = amount (6.23 for example)
this.value = roundNumber(x / 0.05, 2);

---

I think that should do it... You should know roughly what to do with the code

EDIT: An untested example...

js code:

---

<form name="MyForm" action="https://www.paypal.com/cgi-bin/webscr" method="post">
  <fieldset>
    <label for="amount">$</label>
    >>><input id="amount" name="amount" value="5.00" onchange="var id=document.getElementById('result');id.value='Result: $'+Math.round(((this.value*1)/0.05)*Math.pow(10,2))/Math.pow(10,2)"/><<<
    <label for="custom">Steam ID:</label>
    <input id="custom" name="custom" value="<?php echo strstr(curPageURL(), 'STEAM_');?>" />
    <input name="business" type="hidden" value="******************" />
    <input name="cmd" type="hidden" value="_xclick" />
    <input name="currency_code" type="hidden" value="USD" />
    <input name="item_name" type="hidden" value="vip" />
    <input name="no_note" type="hidden" value="1" />
    <input name="no_shipping" type="hidden" value="1" />
    <input src="http://www.paypal.com/en_US/i/btn/btn_donate_LG.gif" type="image" alt="Click here to donate">
   
  </fieldset>
</form>

>>><div id="result"></div><<<

---