addtocart.phtml

<?php if ( Mage::getModel('cataloginventory/stock_item')->loadByProduct($_product)->getEnableQtyIncrements() ){ ?>
	<select class="input-text qty" name="qty" id="qty">
		<?php $i = (Mage::getModel('cataloginventory/stock_item')->loadByProduct($_product)->getMinSaleQty()?Mage::getModel('cataloginventory/stock_item')->loadByProduct($_product)->getMinSaleQty():1);  ?>
		<?php do { ?>
		<option value="<?php echo $i?>">
			<?php echo $i?>
			<?php $i+= Mage::getModel('cataloginventory/stock_item')->loadByProduct($_product)->getQtyIncrements() ?>
		</option>
		<?php } while ($i <= (int)Mage::getModel('cataloginventory/stock_item')->loadByProduct($_product)->getMaxSaleQty()) ?>
	</select>
<?php } else { ?>
	<input type="text" name="qty" id="qty" maxlength="12" value="<?php echo $this->getProductDefaultQty() * 1 ?>" title="<?php echo $this->__('Qty') ?>" class="input-text qty" />
<?php } ?>