Should you need to leave the Secure Payment application, there are two methods available:
Using the Android Back button
Using the Exit menu from the Settings page
From the main screen, touch the Android system Back button, found on the bottom left third of the screen.
Enter the merchant password and touch Confirm.
To exit the application using the Exit menu on the Settings page:
From the main screen, touch the Menu button.
Enter the merchant password and touch Confirm.
Scroll to the Help & training tools section.
Touch Exit.
Touch the Confirm button to exit the application.