I have figured out how to trim the menu items on the web page.
I need to add the following element to the web.config file
<siteMap defaultProvider="XmlSiteMapProvider" enabled="true">
<providers>
<add name="XmlSiteMapProvider"
description="Default SiteMap provider."
type="System.Web.XmlSiteMapProvider "
siteMapFile="Web.sitemap"
securityTrimmingEnabled="true" />
</providers>
</siteMap>
Also I need to specify the roles for ALL menu items.
<siteMapNode url="" title="Mary's Pizzeria" description="Mary's Pizzeria Web Site" roles="*">
<siteMapNode url="Default.aspx" title="Home" description="Mary's Pizzeria Web Site" roles="*" /> ;
<siteMapNode url="order_online.aspx" title="Order Online" description="" roles="*"/>
<siteMapNode url="report\Report.aspx" title="Report" description="Report" roles="admin, customer"/ >
<siteMapNode url="admin\admin.aspx" title="Administration" description="Administration" roles="admin" />
</siteMapNode>