For example
      1.256 rounded to the nearest whole number
would be 1 (because the next number to the
Right “2” is less than 5) so the whole number
stays as it is
       1.568 would be 2 (because the next number
to the right is 5) so the whole number is rounded
up
       5.952 would be 6
Rounding to the nearest 10 follows the same
method
     62 would be 60, 65 would be 70 and 68
would be 70
Rounding to the nearest  on hundred follows
the same method
536 would be 500,    568 would be 600
You can round to the nearest thousand,
ten thousand, hundred thousand, million etc
(always look at the number to the right)

If you are asked to write down a number to
a given number of decimal places by using
The same method as above
5.365 to two decimal places
6 is the second decimal place, the next number
Is 5 so the 6 is rounded up 5.365 to 2 dp is
5.37.   5.364 would be 5.36
You can do the same to one decimal place,
three decimal places etc.
Writing down a number to one significant
number is slightly different
Take the number 43521 and write it down to one
Significant figure 4 is the first number so it is the
most significant 3 is the next number to the right
(3 is less than 5) so the answer is 40000
If the number was 46521 (6 is more than 5) so
the number would be 50000
To two significant figures  52121 would be 52000
and 52621 would be 53000

0.0056 to one significant figure would be 0.006
0.0054 would be 0.005