Yes gift received from sister is fully exempt. The cash transaction limit per day is Rs.2L and therefore there is no tax or penalty on cash gifts received from sister.
However, the receipient shall disclose such gift in his ITR as exempt income.
Prepare Gift Deed ,Exempt under section 56(2) of the Income tax act 1961 in the hands of recipient in case of relative ,as Jain sir already sated above .