Our store includes quantity discounts which, when shown in 2dp (2 decimal points) often fail to calculate properly for low value items such as standard/straight blunt needles. To counter this and make discounts (and currency exchange rate differences) clearer we decided to show unit prices in 3dp (3 decimal points). This allows differences to show far more clearly and allow a better understanding of how quantity affects order pricing.
Of course, when it comes to understanding the final totals and processing some confusion remains on the cart and checkout views. We have do convert the order Sub-totals and Totals on these pages to 2dp, to show the overall charge to be applied, but the store system doesn’t allow this for lines (eg: shipping cost) so it’s not perfect, but given the limitations it’s the best we can do at present.
Short version, you get better quantity discounts than we could offer with just 2dp rounding.