i-Reserve works with rounded amounts. You cannot get around this, since working with more than 2 numbers after the comma is not common and not clear. In i-Reserve the amounts are rounded off on the basis of detail rules. Initially amounts incl. VAT are included, after which the VAT in this amount is calculated on the basis of the entered VAT rates. The VAT is then deducted from the incl. VAT amount to calculate the total price excl. VAT. The total amount is rounded off.

To ensure that the rounding is indeed official and legal, the rules of the tax authorities are used.
More information about this can be found on the page of the Dutch tax authority.