4000
People who do not understand bias will say round all 5s up and so the answer should be 5000.
People who do understand bias will argue that you should round 5s up or down roughly half the number of times. One way of achieving this is to make the last "surviving" significant figure even. In this case, round down to 4000.
4600
378000
161,280 Rounded to the nearest thousand is 161,000 Rounded to the nearest ten thousand is 160,000 Rounded to the nearest hundred thousand is 200,000
66667000
6172000
157 rounded to the nearest thousand is o
5000
5000
4500 can be rounded only to 4500 to the nearest 100.
4500
4500
4500
4500
4540
4500
4500
4500
63795 rounded to the nearest thousand is 64,000