working out exchange rates rounding up or down

Example. If i purchase shares for $150 with an exchange rate of 1.766 The calculator gives £84.937712344 What do I round it to, £84.93 or £83.94?

Hi JamesMay75,
You round the amount down to £84 as the system would do that anyway for you. 
Thank you. 

I meant in working out computations not for the final input figure to HMRC. would i round up or down an amount from US dollars To GBP. For instance if i bought the shares in us dollars and i worked out the cost per share was £84.755, would i put a share price in my computations as £84.75 or £84.76

Hi JamesMay75,
Round down to £84.75
Thank you.