Re: The Warden...
Well I do not recommend hiding things from your wife, that's not a great practice to get into... but for the sake of minding my own business and getting you the info you need... use your cash to buy a pepaid debit card.
Amex, visa, mastercard (gift cards)... just make sure you got enough for your purchase on there or it won't go through.... like $100.00 visa gift card for a 70.00 purchase. Then use the other 30.00 for groceries or a gift for her (but not on gas unless it's prepaid inside)
I'm pretty fluent in gift cards, but because I get them from my coupon shopping.