Free shipping is available with minimum $25 spend (after voucher) with Shipster. Enjoy :)
• Shipping not included. Free shipping for orders over $50
• Valid for online redemption only
• Limit of 2 vouchers per person
• Purchase up to 1 additional as a gift
• Max 1 voucher per transaction
• Cannot be used in conjunction with any other voucher, coupon or gift card
• Not valid for prescription medications
• Not valid for Flu Vaccination page
• Redeem online by: 31 Mar 2019 (11.59pm AEDT)
No idea if cashback applies as Groupon may consider this to be a value voucher. You have nothing to lose by trying :)
Except second point in that post:
Or from cashrewards web site