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I think 10 Mbps Ethernet is 10,000,000 bps, not 10,485,760. However, if you're dealing with a logical bandwidth limit, it depends on what value your provider is using. Also, when enforcing a bandwidth limit, measurement interval become important, and those too are up to how your provider is configured.
Additionally, 10 Mbps is the raw transmission speed of the Ethernet. It doesn't include L2 or L3 overhead. So, again, it's up to your provider to determine what their 10 Mbps bandwidth limit means (they should be able to tell you what/how they are measuring).
Years ago, I worked with a Tier 1 provider, whose logical limits attempted to simulate Ethernet wire rate for that "bandwidth". I.e. if you had a 10 Mbps cap, useful bandwidth should be like original 10 Mbps Ethernet.
On Cisco routers (including 2811s) I would usually shape about 15% slower, as I believed most Cisco shapers don't account for L2 overhead. (The 15% is about L2 overhead for average packet sizes. Overhead percentage, though, varies with frame size.)
