At work, I have the option of signing up for health insurance that covers sterilization and abortion. Would it be wrong for me to sign up?

No, it would not be wrong for you to sign up. Your intent is to pay for medical coverage for yourself and your family, not to pay for abortion or sterilization. Of course, if you can find comparable coverage and rates through a company that does not cover abortion or sterilization, it would be better to buy your coverage from that company.