it looks like you are using a 2columns-right
template in your cart, try this one :
app/design/frontend/{package}{theme}/layout/local.xml
<checkout_cart_index>
<action method="setTemplate"><template>page/1column.phtml</template></action>
<checkout_cart_index>
If it doesn't work try this:
Go to : app/design/frontend/{package}{theme}/template/checkout/cart.phtml
then move <?php echo $this->getChildHtml('totals'); ?>
to :
...
</tbody>
</table>
/*Here*/
<div class="row">
<div class="col-md-6">
<?php echo $this->getChildHtml('totals'); ?>
</div>
</div>