VAT Strange Behaviour!!

Hi



I have VAT set to 17.5% and on my products it displays as this



Price: £43.40 (£50.99 inc tax)



I have tried a few VAT calculators and it should be £51 so ideally it needs to be rounded up to (£51 inc tax) to make things worse on the checkout page it does round the price up to £51.



Any ideas or help on this.



Thanks in advance

Karl