It is still 2970 although, if you wanted to show that it was accurate to the nearest 100th you could write is as 2970.00
2970.000
It is 300 when rounded to the nearest hundred
916 rounded to the nearest hundred is 900
5800
0
It is already rounded to the nearest hundred thousandths. Rounded to the nearest thousands would be 87.381.
0
10000
0
0
678 is rounded nearest hundred is 700