>>Does hockey wagering involve a dime line, or is it 20 cents across the board?
Generally 20 cents, although some reduced vig shops like Pinny will have cheaper prices. Although, Spinner had dime NHL for a few months ... perhaps coincidentally or not
they are no longin in Biz (they were aquired)
>> Is baseball the only sport which has a dime line at many books?
Yes, but some reduced shop are IIS, Canbet, Pinny, BAS, BetPanam & surely others that I don't know of.