you would need to create a new column in the eCart object called taxable.
for items that have tax applied, set the value of the taxable column to 1 in the add to cart object.
for items that should not have tax applied set that column to 0 in the add to cart button.
you can then create your tax rule using the trigger "Number of items with a specific column value":
if the total number of items where 'taxable' has a value of '1' is '>' a value of '0'
and the calculation:
based on items with a specific value:
total of 'TotalPrice' where 'taxable' has a value of '1' 'times' '0.82'
you can substitute your tax rate for 0.82.