quantity causing sub cent amounts causes validation errors

[langalex]

When creating a line item with a quantity that leads to sub-cent amounts, i.e. net = 1.13, quantity = 0.1, then net * quantity = 0.113. This leads to a validation error here, because summed_tax_base_amount is not rounded (i.e. it's 0.0113), whereas the tax_amount, that I pass to the invoice, is rounded to 0.01.

[halfbyte]

@langalex Released 3.8.1 with your fix. Thx, good catch!