2004 Nissan Sentra Fuel tank

My car's fuel tank intake has been apparently blocked for about 4-5mths, as everytime I have to fill up with gas. It only takes about a dollar of gas at a time. Bought my car new off a Nissan dealer 5yrs ago and about two yrs after, had to replace the fuel pump once--did so directly at the same dealer of purchaser. When this new problem arose, had a mechanic look at it about a month after, and after prodding and testing- he advised a new fuel tank was the only solution. As he didn't find anything clogging the intake hose, etc. I am assuming he also checked to see if I simply needed a new fuel filter. Any idea what else it can be and will I most likely need to replace the fuel tank?