GST appears to not be Calculating Correctly

I have an invoice that I am matching to a PO and it works perfectly - all values agree to the penny - except for the GST / TAX

The total dollar value of the invoice line items is 9,321.81 and at 5% GST would be 466.0905

When I look at the number GP (2015 R2) presents, the GST is 466.1350

Now we are not going to lose it over .04 but the important question is why.

What we know:

There are 40 line items

All 40 have GST - same tax detail - attached

When I review each detail line I get a total of 466.135

Anyone have a suggest as to why and that can be explained to a client that is a little concerned about how the system works already and now we see this happening.