http://onionq2p24l4dshdixymmqk5bo3iar4sbama5uwcc7nz45vpio6xlxqd.onion/basic-theory-2
Bob knows you sent it and assumes address B is also your (because it is rare to
pay uneven amount like 4.99 and get round 5 as change).
He may suspect address A is yours but he is not sure.
If you pay for coffee with 4.99 mBTC address barista will not know if you
also own 5 mBTC. This single transaction increases your blockchain privacy and you can
repeat it many times.