“Good Karma Jar” is another name for a tip jar, where that name or “Tipping Is Good Karma” has been printed on stickers. A March 1995 New York (NY) Times article on coffee bar tipping included the tip jar signs “Tips create incredibly desirable karma!” and “Karma is a boomerang.”
 
“Tipping is good karma” has been cited in print by at least 1996, and “karma jar” by at least 2000.
       
 
New York (NY) Times
Coffee-Bar Tipping? The Jury Is Still Out
By DAN SHAW
Published: March 1, 1995
THE coffee of the day is usually hazelnut, and the question of the day is whether to tip for it.
 
All over Manhattan, coffee-bar patrons are being confronted by jars and bowls with signs like “Tips create incredibly desirable karma!” and “Out of pity, out of generosity, whatever! We don’t care. Tips!” And many New Yorkers, only recently having mastered the art of ordering espresso and lattes, are confounded by this facet of coffee-bar culture.
(...)
Liora Simpson, the marketing manager for the Dalton Coffee Ltd. shops in Manhattan, all 10 of which have tip jars with the slogan “Karma is a boomerang,” said employees didn’t depend on tips. “It’s an extra bonus for them,” she added.
 
12 July 1996, The Orange County Register (Santa Ana, CA), “Coffeehouse has some reasons for you to give” by Elizabeth Evans, Show sec. pg. 40, col. 3:
Tipping is good karma.
 
Google Groups: alt.fan.miss-manners
Tipping at coffee shops
Heather Garvey
1/24/00
(...) 
The Ben&Jerry’s here has a “karma jar” for tips. Now, this is an extremely hippie-esque place, where I’m sure they go on about The Man in the back or somethingand you can feel the ‘tude if you don’t tip, and
I always want to say “Why the hell don’t you pay your people enough so they don’t have to solicit for tips? Wouldn’t that be more Earth-friendly?”
 
Google Groups: rec.music.phish
“Karma Jar” (NPC)
jacob lake
8/8/00
Hey everyone,
I have noticed something that I want your opinion on.  I am not well versed in the religous aspects of Karma, or the major religion it is affiliated with, but I do believe a lot of the circular pattern of vibes (what comes
around goes around, get what you give, etc). Anyway, I go to a bagel shop every morning.  There is a new girl working there, and she is, by my estimation and speaking with her a “pseudo head” (a fake head)*.  So, she put a jar out for tips, and it is called the Karma Jar.  Every morning, I want to tell her that Karma is not (IMO) a financially driven venture.  I may bring a necklace in to hook her with soon.  What are your thoughts? Should this “tip jar” be labeled the “Karma Jar”?
   
Google Groups: alt.fan.miss-manners
Tip jars and owners
Heather Garvey
8/23/00
(...)
My local Ben & Jerry’s amuses me. B&J are so “we are the world” in image, and yet they apparently don’t pay their people a living wage, as they have large, colorful “tipping is good karma” jar hogging up most of the space in front of the register. I’m tempted to write a note saying “Try paying your people a decent wage, capitalist pigs!” and dropping it in the jar. 😊
     
Google Books
The Sad Truth about Happiness
By Anne Giardini
New York, NY: Fourth Estate
2005
Pg. 97:
“Thank you,” I said, surprised, wondering if this was a new imprecatory gimmick, like the little handwritten “Tipping Is Good Karma” signs I had seen taped to bowls beside the cash register at coffee shops.
 
Google Books
May 2007, Cincinnati Magazine (OH), pg. 86, col. 3:
The guy who whips up my drink has no hair on his head but plenty on his chin, and the concoction looks so good I plunk a dollar in the tip jar, or rather, the “karma jar” as a small paper sign notes.