its it correct proced ? 

If the number is -90.10 and after rounding off  / it become 90 , is it right ?

 

You can round a number to the nearest tenth, hundredth, thousandth etc. by looking at the last digit to keep. If the next digit is less than 5 then you leave the number to the predecessor and  If the next digit is greater than 5 then you leave the number to the successor.

90.10 can be rounded off as 90.

90. 60 can be rounded as 91.