Custom TaxClassInfoProvider

I have copied nearly verbatim (aside from changing the class names) the sample code to create a custom TaxClassInfoProvider and is not working. Here is my code:

CMSECommerceModuleLoader.cs

using CMS.TreeEngine;
using CMS.SettingsProvider;
using CMS.DocumentEngine;
using CMS.EventLog;
using System.Text.RegularExpressions;
using System.Linq;
using System.Xml.XPath;
using HtmlAgilityPack;
using CMS.SiteProvider;
using CMS.CMSHelper;

[ECommerceModuleLoader]
public partial class CMSECommerceModuleLoader
{
    private class ECommerceModuleLoader : CMSLoaderAttribute
    {
        public ECommerceModuleLoader()
        {
            // Require E-commerce module to load properly
            RequiredModules = new string[] { ModuleEntry.ECOMMERCE };
        }

        public override void Init()
        {
            ClassHelper.OnGetCustomClass += GetCustomClass;
        }

        private static void GetCustomClass(object sender, ClassEventArgs e)
        {
            System.Web.HttpContext.Current.Response.Write("GetCustomClass");
            if (e.Object == null)
            {
                // Provide your custom classes
                switch (e.ClassName)
                {
                    case "FranchiseTaxClassInfoProvider":
                        e.Object = new FranchiseTaxClassInfoProvider();
                        break;
                }
            }
        }
    }
}

FranchiseTaxClassInfoProvider.cs

using System;
using System.Web;
using System.Data;
using System.Collections.Generic;

using CMS.DataEngine;
using CMS.Ecommerce;
using CMS.SettingsProvider;
using CMS.SiteProvider;
using CMS.GlobalHelper;
using CMS.CMSHelper;

public class FranchiseTaxClassInfoProvider : TaxClassInfoProvider
{
    protected override DataSet GetTaxesInternal(ShoppingCartInfo cart)
    {
        System.Web.HttpContext.Current.Response.Write("GetTaxesInternal");
        DataSet ds = new DataSet();

        // Create an empty taxes table
        DataTable table = GetNewTaxesTable(); 

        foreach (ShoppingCartItemInfo item in cart.CartItems)
        {           
            AddTaxRow(table, item.SKUID, "Franchise Tax", 10);
        }

        // Return built dataset with the taxes
        ds.Tables.Add(table);
        return ds;
    }

    private DataTable GetNewTaxesTable()
    {

        DataTable table = new DataTable();

        // Add required columns
        table.Columns.Add("SKUID", typeof(int));
        table.Columns.Add("TaxClassDisplayName", typeof(string));
        table.Columns.Add("TaxValue", typeof(double));

        return table;
    }

    /// <summary>
    /// Creates tax row which holds the data of the tax which should be applied to the given SKU.
    /// </summary>
    /// <param name="taxTable">Tax table the row should be added to.</param>
    /// <param name="skuId">SKU ID</param>
    /// <param name="taxName">Tax name</param>
    /// <param name="taxValue">Tax value</param>
    private void AddTaxRow(DataTable taxTable, int skuId, string taxName, double taxValue)
    {
        DataRow row = taxTable.NewRow();

        // Set required columns
        row["SKUID"] = skuId;
        row["TaxClassDisplayName"] = taxName;
        row["TaxValue"] = taxValue;

        taxTable.Rows.Add(row);
    }
}

As you can see, I'm still only testing and trying to add 10% to each item. What am I missing? Should this just be working now or is there something else I need to do? Thanks!