Costco
Double taxation on costco coupons

I had four store discount coupons total about $12.50. The subtotal before discount applied and taxed was $82.44. Then it was taxed for $6.39 (CA 9.75 tax) for a grand total of $88.83. Then my total coupon discount of $12.50 knocked off my total for $69.94. This part is understandable to me whenever I used coupon I pay the taxes. However, COSTCO went further by adding my previous total taxes of $6.39 to the $69.94. The total became $76.33. Why was my bill added two times the total taxed amount ($6.39)?

Company: Costco
Country: USA
State: California
City: San Dimas
Address: 520 N Lone Hill Ave

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