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Item level coupons can be added to single items when using the drop down feature. So coupons will have to be created on the CAS before. Coupons used here will be noted as a coupon transaction and noted under coupon transaction report. 
How are discounts and coupons taxed?
Line item coupons and all discounts are treated as a reduction in the selling price. If a price is listed as $20 and there is a line item coupon of $1 or a discount of any kind the taxable amount is reduced by the coupon/discount before the tax is calculated.
Transaction level coupons are treated as tender so the tax calculation is before the deduction.
Access
Is at a POS level, for POS users.