rounding / calculating problem

-- HikaShop version -- : 2.6.0
-- Joomla version -- : 3.4.4
-- PHP version -- : 5.3.29

hi,

i have an problem with rounding in hikashop

as you can see, 0.05 x 3 is 0.16 instead of 0.15 euro

so we've in germany an Tax Rate of 19%, if the price with tax 0.06 euro, hika calculates a price of 0.050420168067227 without taxes, if i put 0.05 into the price without tax, hika calculates a price of 0.0595 euro.... i guess there is the problem in my case, i would like to change the calculate routes that hika is rounding to the second number after the comma

how can i do that?