Pronunciation of "often" [duplicate]
"Should" is inappropriate in the question. Both pronunciations occur.
In the 19th century /ɔ:fn/ ("aufn") was the normal pronunciation, so in The Pirates of Penzance, there is an elaborate joke on the confusion of 'often' and 'orphan'.
In my dialect, it's "I of-en go to the store." If you say "off-ten" it's like you are enunciating particularly clearly for some reason. It's possible that "off-ten" is normal in other regions, though.