The answer depends on the units used for the given quantity. It should be plainly obvious to anybody that the answer for 6.49 cents will be very different from that for 6.49 dollars. So, without any information about the units for the given quantity, it is not possible to give a sensible answer.
650
649 rounded to the nearest 100 would be 600. Once it reaches 650 though, it would round up to 700.
600
649 rounded to the nearest hundreds place value would be 600.
600
To the nearest thousand: 3000 To the nearest hundred: 2600 To the nearest ten: 2650 To the nearest one: 2649
649
600 as it is 49 away from 600 but is 51 away from 700
649
To the nearest ten, 650 To the nearest hundred, 600 To the nearest tenth, 649.0
600
To the nearest whole dollar, it is $358.