durations calculated from different start/end times multiplied with h rate and VAT differ

[IdrNiz]

For project time tracking the customer wants a simple table with one line per day.
Different start/end times which result in the exact same duration, lead to a difference after being multiplied with the hourly rate and the customer-specific discount, resulting in a difference of 1 cent when calulating VAT. 

Would like to understand where the difference comes from. 

Thanks in advance. 

[#2]

Use Round formula with 3 digits and reduce digit to 2 through home tab

[#3]

Thanks, Safy84. Yes, that results in same values.

Unfortunately, it does not explain the cause.

[#4]

@IdrNiz