Most taxes are actually not based on the base fare, they are usually fixed depending on the destination, transit or departure or arrival, a few depend on cabin of travel and indeed some depend on the fare, but all are listed with 2 decimals for the EUR market. For legacy carriers, published fares follow rounding rules set by IATA at market level. For instance in the EUR zone as point of sale, fares are rounded to the nearest (or higher?) EUR, so there is never cents in the fare basis. Also fares published in EUR are published in full EUR. Air Baltic is the only "legacy carrier" that is a little different since its web fares do not follow this rule although its published fares bookable from a travel agent follow this rule.