order totals and sales tax aren't adding up

[fbmstar]

I've been entering some Ebay purchases into a spreadsheet and noticed the order totals on a couple of items aren't adding up.  In the first picture below, the total is actually $13.59 when adding the individual lines, but I was charged $13.74... About 1.1% difference.  On top of that, I think I was charged too much for sales tax.  It is 6% in my state, so sales tax should be $0.77, not $0.78.

This second picture was an order from oversees and the order total here adds up to $265.17GBP when adding the individual lines, not $268.17GBP as shown.  The sales tax is off on this too and should be $15.18, not $12.90.  When I add it all up with the correct sales tax, the order total is accurate.

Would appreciate any info you all might be able to provide on why these numbers aren't lining up.  I just checked 10 random orders, and the numbers do line up on those.

thanks,

[kathiec]

@fbmstar 

Did you take tax on shipping into your calculations? A number of states also tax shipping. Were the 10 random orders you checked all free shipping?

[fbmstar]

Yes, shipping was included for tax calculation.

[eburtonlab]

On top of that, I think I was charged too much for sales tax. It is 6% in my state, so sales tax should be $0.77, not $0.78.

Minor differences in sales tax -- on the order of a cent or so -- can be due to different rules for how sales tax is calculated when multiple items are being purchased. Some states require sales tax to be calculated per item rather than being calculated on the total amount, which can lead to different results due to rounding of small amounts.