Sale of shares by fifo method

I would like to know is it mandatory to sell shares in stock market  as per FIFO... or we can sell any scriptt with lower cost n make suitable gain.

and while doing accounting in tally for this transaction of sell, is it mandatory to follow FIFO method for share scriptt or we have to do accounting as per actual sale of scriptt(which is nt FIFO basis) & account Capital gain / Loss.

Pls advice.