Don't see anything about a minimum gift amount to qualify for the free $5. Here is the fine print:
Amazon Birthday Gift "Try It Now and Get $5" Promotion: Terms and Conditions
In order to qualify for the promotional credit:
You must purchase 1 or more gifts through Amazon Birthday Gift during the promotional period (between 2:00 PM PDT on Friday, August 23 and 11:59 PM PDT on Sunday, September 22)
1 or more gifts must be successfully delivered to the birthday gift recipient within the promotional period
You must have an Amazon customer account that has been in good standing for at least 30 days prior to purchasing the gift through Amazon Birthday Gift during the promotional period
You must have connected your Amazon customer account to your Facebook account to purchase a gift through Amazon Birthday Gift, and keep these accounts connected through the gift delivery date.
The promotional credit you qualify for will be automatically applied to your Amazon customer account, no later than 5 business days after the end of the promotional period (September 27, 2013). You will receive an email confirmation at that time.
The promotional credit will be reflected as a $5 savings on the Review Your Order page on qualifying orders.
The promotional credit may only be applied to physical products shipped from and sold by Amazon.com, and excludes digital downloads and gift card purchases.
Your promotional credit expires at 11:59 PM PDT on September 30, 2013.
If items purchased with the promotional credit are returned, the amount of the promotional credit used to purchase such items will be subtracted from your return credit.
The promotional credit is non-transferable and may not be resold.
The promotional credit may not be combined with other Amazon Birthday Gift offers.
If you violate any of these Terms and Conditions, the promotion will be invalid.
Limit one promotional credit per customer, Amazon customer account, and Facebook account.
Void where prohibited.
Amazon reserves the right to modify or cancel the promotion at any time.
Thanks....not worth using the deal