How to fix the Invoice module's total amount?
It is not a mistake. That moduo do rounding. See the photo:

Subtotal: 134.50
VAT: 25.55
Total: 160.06

So, the real value of VAT is 134.50*0.19=25.555 and real total is 160.055 but for invoices you need to do rounding at two decimal places. And you get total 160.06.