i think its in half-step-down tuning. I know its right, regardless
intro
e|-------------------|
B|--9----6---4-------|
G|--9----6---4-------|
D|--9----6---4-------|
A|-7-7-4--4-2-2-3-2--|
E|-----------------0-|
[ Tab from: http://www.guitaretab.com/n/nirvana/13410.html ]
verse
e|--0------0-----0------0---|
B|--0------0-----0------0---|
G|--9------6-----4------5---|
D|--9----6-6-6---4-----5--5-|
A|-7--7-4------2---2-3------|
E|--------------------------|
chorus
e|----------------------------|
B|----------------------------|
G|-------2-2-2-9-9-9-6-6-6--5-|
D|-5-5-5-2-2-2-9-9-9-6-6-6--5-|
A|-5-5-5-0-0-0-7-7-7-4-4-4--3-|
E|-3-3-3----------------------|