it depends...every bank gives u a different rate....u will have to find out the best rate. some banks try to keep a fixed rate, some say they will charge whatever the rate is at the time of transaction.
reatil transactions are done on higher rate , FOR EXAMPLE ; if its 54 on google thn reatil rate mst b 55 .... so dont depend on google or other softwares ... u have to ask foreign exchange people about this or from banks