How to change the redirect page after an approval response.

Add a 'source' query string parameter to the approval link. For example, instead of just using the ApprovalUrl token to construct the link, add the following to the end of the URL: &Source=http://destinationlocation 

Note: This will only take affect when using the link in the email notification. When accessing the task from links inside SharePoint, SharePoint adds its own source= parameter for redirects.