First: set up Tax Rate (under Tax)
Second: For each product, select the appropriate tax rate in the VAT id drop down on the Product Information page.
Third: Check that your default shopper group is set to Show Prices including tax (or not, as you wish). Set up other Shopper groups as desired (e.g. Retail to show tax, Wholesale not to show tax).
In all cases, provided you have a tax rate of more than 0, there should be a Tax Total showing on the Cart Checkout page.