33,500,000 to 34,499,999
All numbers can be rounded to the nearest ten.
An infinite number.
88500
530
Infinitely many numbers.1 million and 1 whole numbers . Although, technically 34 million, itself, would not be rounded. This would comprise the numbers from [33,500,000, 34,500,000]. In the first case the 5 is rounded up while in the second it is rounded down. This is consistent with the rule of "Round up or down so that the new last digit is even". This is the default rounding mode used in IEEE 754 computing functions and operators.
There are infinitely many such numbers.
1000
999 of them.
70
70
340
It depends on whether you are rounding to the nearest integer, nearest 10, nearest 50 etc.