Why is Final Value Fee on $20 stamp sale $1.23 and not $1.20 (6% of sale)?

[hillam-sales-online]

Have final value fees gone up recently? I have a basic store and sell US stamps in auctions. Until recently, my final value fee was simply 6% of final sale price. (I always do free shipping.) So why am I being charged an extra penny or two or three per sale? What's the EXACT calculation? I obviously need to revise my spreadsheet where I calculate my exact costs and profits.

[partial*eclipse · Accepted solution]

The rate went up to 6.15% on May 1.

http://pages.ebay.com/help/sell/storefees.html