Yes, you can do it now on every order. Here is how: when checking out on Magestore, if you click on Recommend button to share your purchase with Facebook friends, your Order total will be automatically deducted $5.
You can buy excellent Magento extensions and themes at MageStore. Go to Promotion Programs to look for other discounts and promotions too. For example if you buy more than one extension you can get 20% discount.