How do i close my safari browser after visiting banking sites?

To close tabs, tap the X on the left side of the tab. In order to close the last tab in Safari, tap the double squares icon in the upper right corner and then tap the X on the last tab in that window. in order to close the app completely, double tap the home button and find the Safari preview to the left on the screen and swipe up on that preview to flick it off the top of the screen. Tap the home button when done.

IF you are still concerned about security, go to Settings>Safari>Clear History and Website data.