Quick steps on how to redirect back to your magento store upon a successful purchase. Unfortunately, you can only redirect to one page.

Sign into Paypal account
Click directly on Profile -> Website Payment Preferences
Change Auto Return to on.
Fill Return URL to http://www.mymagentositregoeshere.com/checkout/onepage/success/
Save and then go test it!

After a successful paypal payment the customer will be redirected back to the magento order success page. Hope this helps!