computations and 104 holding

when working out 104 holding what is the process i should follow when showing my computations? if i buy 10 shares at £12.77 do i put this as a pool cost of £127.70 , £127 or £128, I ask as i am adding up my 104 pool cost over the years and wanted to know if i always round the figures for every transaction then add it to the previous pool cost? what i am in effect asking is, i have lots of transactions to add up over the years which will change my 104 holding cost of acquisition. do i round up/down for every purchase to whole pounds before adding to the 104 holding or do i include any pennies basically am i allowed to use pounds and pence in my computation sheets?

Hi
Round up .