Item Taxibiilty - Functioning inconsistently

Hi All,
I am working with an Items with their Purchasing Item Attributes indicating Taxable, however, when I source these items into a Purchase Order the items are defaulting to Tax Exempt. I have verified that the items' attributes indicate Taxable, that the vendor associated to the item is set to Sales Tax Applicable and that the shipto location calls for sales tax. Any thoughts?

Appreciate any insight.

Thanks in advance,

CM