NJ Laws and Firecodes do not allow you to pump your own gas in NJ. When you receive gas in NJ you should not tip or in better terms it is not necessary. In another state you should INDEED tip if you pull up to a full service pump when self service is an option.
More NJ recommendation - you are not paying for full service in NJ, in many cases you are paying less than self service in another state. Do not expect your attendants to clean your windows and check you oil. Especially in the RAIN or SNOW. If you ask for these services you better TIP in NJ!
Also watch the pump dollars before you begin getting fuel in NJ, make sure it is set to $0.00 other wise you are getting ripped off $1.00 (good NJ scam). The scam works by resetting the pump to read $1.00 and proper gallons for $1.00 before the next car arrives....this works on OLD gas pumps and I have not seen it done on DIGITAL. Avoid analog pumps. Buying oil? Make sure you are buying what you paid for .... just because the oil container says MOBIL it may not contain a Mobil oil - this will cost you an extra $1.50. Oil scam works like this ..... the gas station attendants goto K-Mart and buy a case of cheap no name oil for 69 cents a quart. Then they collect empty ligitimate bottles of oil from the gas station and refill the bottles with cheap oil. The oil is then sold at regular price of $2.50 - earing the attendant a little under $1.50.
I worked at a few gas stations in NJ while in college('97) and highschool('93) (ages 17, 19, 20). There are many scams at the stations - an attendant can make up to $100 a day scamming. This pays for hot lunches in the winter, and cold drinks in the summer.