As long as there is (semi) disposable income after the bills are paid, my wife and I don't audit each others books.
We're both savvy bargain hunters, so we trust each others judgement. I don't bother her when it comes to shoes, jewelry, housewares. She doesn't bother me with bikes, computers, and tools.
We've had tight times in the past, so I tend not to spend much without "clearing it" with her, not so much to get permission, as to make sure it won't bounce a check. We bounced some a month or two back; she got a bonus check and paid ahead on bills.... a little too much, and forgot about an automatic withdrawal she set up.