Getting ice and charge minimums

I don't know if I'm the stupid one in this tale, but I thought I'd relay my shopping experience of yesterday.

Cinda, Clarisse, and I headed out to Sarah's with our ice cream maker, batter, etc. We had everything but the ice (2 bags needed) which we planned to pick up at the last minute to minimizing melting in transit. Stopped at a BP station, Cinda parks, I get two bags of ice and then wait in line to check out. "$3.00" says the clerk. I hand her my credit card. "Credit or debit?" says the clerk. "Credit," says I. "We have a $5.00 minimum," says the clerk. "Then debit," says I. "We have a $5.00 minimum," she says again. I check my wallet for cash as a line is forming up behind me; I have a single dollar bill. "I only have a dollar," says I as I show her this fact. She gives me deer-in-the-headlight eyes; "We have a $5.00 minimum." Now clearly, I am supposed to go find another $2.00 worth of purchases and then get back at the end of the line (which is now about five people long). Instead I gave her the two bags of ice and walked out. I bought my ice two blocks down the road at the grocery store for $0.25 less a bag.

Cinda tells me she could have gotten gas and doesn't seem to understand my insistence that I will not be coerced into spending almost twice as much by some store clerk and her policy. Especially after she has already accepted the card and asked me "credit or debit?". There was no notice of this minimum charge policy either; I looked.

I understand that, with the way the charge companies work, it might be desirable to have minimum charge policies. And, as I did in law school, I do change my shopping habits to avoid spending money in places with minimum charge policies. As long as they save more money avoiding less than the minimum charge than I would spend their they made the right call. but I am not a sheep and I can, and do, express my opinion with where I take my business. In the circumstance at BP, with the line piling up and having already taken the card for the $3.00 purchase, the clerk should have either 1) run the card anyway or 2) taken the dollar in cash and be done with it and on to serving the next customer, especially when ice is cheaper just down the street.