<input type="hidden" name="cmd" value="_xclick">
<input type="hidden" name="amount" value="5.00">
<input type="hidden" name="no_shipping" value="1">
<input type="hidden" name="currency_code" value="USD">
<input type="hidden" name="tax" value="0">
<input type="image" src="https://www.paypal.com/images/x-click-but21.gif" border="0" name="submit" alt="Make payments with PayPal - it's fast, free and secure!">
</form>
That should work fine tho i will say that you should rethink this.