You know what I like doing at my shop? (The newly named Purple Squirrel.) I like saying to my customers, "Your total comes to 15.73, please." And when I give them their change and/or merchandise, I tell them "Thank you, and please come back." These are words that I so seldom hear in a retail experience, and that I take particular notice of it.
In my opinion, the customer is what makes my shop exist. Small pleasantries such as welcome, please, and thank you are part of the retail experience. A person may not buy anything that day, and that's okay. I do and say the same things. But if the ambiance of the store is good, that person will likely go back to that place, or at least tell their friends how nice that shopkeeper was.
Just my little opinion of the day. Small acts of kindness help to make another person happy.