Traditionally the groom's parents pay for the rehersal expenses including dinner. For the wedding proper the groom pays for the minister, flowers for bride and bridesmaids and token gifts for ushers and groomsmen. This is for a full bore traditional wedding.
If her parents/guardians are too cheap to marry off their daughter in style you have no duty to foot the bill.
The groom don't care anyway he just wants to get it over with and on to the more inportant stuff.
