At the 'Stage' selection screen hold 'Shoot' on Ryu and then press 'Right', 'Right', 'Right', 'Left'. If the code has been entered correctly you will hear a confirmation sound and Mega Man will no longer have a helmet at the 'Stage' selection screen.
Use your E-tank to refill your health back to maximum just before killing a Boss. Doing this fools the game into thinking you have earned a 'Perfect' in the round which you will get once you have killed your stage boss.
Intentionally die and remain idle allowing the timer to reach '0'. When you now resume the game you will have ALL the tanks that you previously collected and you will be able to recollect those same E-tanks and add them to your total.