I have a Nordstrom credit card and just got a notice regarding policy changes, what should I do (see details)

I have only used the card once, and don’t plan to use it again. I got a letter saying that they are making changes (as of 12/1/10) to the minimum monthly payment:
”...the formula used to calculate the current due portion of the minimum monthly payment will change which may cause your minimum monthly payment to increase…. the current due each month will be the greatest of (i) $35, or (ii) 5% of my new balance rounded to the next higher whole dollar amount…. and it keeps going

Will canceling it affect my credit? Or will it be more detrimental to keep the account open?