It really depends on what sort of call rate you are using.
We run 6Mbps on private WAN links and I consider anything over 0.5% to be unacceptable. When using the internet, I'd hope that during non-congested periods you were getting similar results. While your connection has congestion you may well get packet loss, but I would hope you would do much better than 5% when there's no congestion - you could be looking at a duplex issue or something.
Not sure about graphing loss over time, sorry.