Hi,
I suppose that in your product, you've set a price of 0.33333 and not 0.33. Thus, the calculation goes like this: round(0.33333*10, 2) = round(3.3333,2) = 3.33. So the calculation is not wrong. Just not what you expected.
You should either set a price of 0.33 in your product, or turn on the "round prices during calculations" setting of the HikaShop configuration if you want the system to use the rounded unit price for the multiplication of the quantity.
Note that you should first contact your accountant regarding that. Based on the laws of your country, rounding (or not) during the calculations might be required.