I did use the gift cards at Target to pay for my cruise, although I didn't get an extra 5% off coupon at any time. My only word of advice is keep all the cards! Any money that gets refunded to you will go back on those cards.
I used 72 cards to pay for our upcoming cruise. A few weeks ago, significant Florida Resident rates came out, and I switched to that. Over $2000 got refunded to those cards. Thankfully, I had them all tracked on my phone on the Disney gift card app, and had numbered them for easy tracking. I renewed APs with them, we went to a few dinners, bought some Christmas presents, paid my tips, set aside spending money for the cruise ... Thankfully, since I live so close to Disney, they were useful to me anyhow.
I was very thankful we had kept them all and numbered and tracked them. I think I wouldn't have been as happy if there wasn't a way for me to use them. Less than $100 was refunded to my bank account, even though my debit card was my last method of payment.