Are you talking about an active listing for sale? Or something that has sold already? If it's listed for sale, your agent should have made the price change in the MLS, and eventually these sites will get updated. Or your agent can manually update the list price.
If you're talking about the sales price of something that has already sold....I'm not sure why you need to change the info on that. This is just a marketing website and the data here is often inaccurate. The sale of your property will be reflected in your county records.