how to round off decimal numbers

Hi Ilakkiya and welcome to the Forum

It looks (from cell E3) that you want to round the number to the nearest 0.10 (so ignoring the second decimal place).

I would use the MROUND function where the second argument (in bold below) is the multiple to which you want to round. The formula in E3 becomes:

=MROUND(D3,0.1)

(but I can't see how the 862.4 in E4 relates to D4 or C4).

This has the advantage that you can set the multiple to suit tricikier situations, e.g. you could round to the nearest 0.25 or 3 say).

Most people however would use the simpler:

=ROUND(D3,1)

(where the 1 in bold is the number of decimal places) and format the display yo show 2 decimal places or currency.. Note that there are ROUNDUP and ROUNDDOWN function which force the way the number is rounded.