Buy Three Types of Stamps Five Each

Yesterday my mother asked me to buy some stamps. Stamps are available in 2paise, 7paise, 10paise, and 15paise and 20paise denominations. For three types of stamps I was asked to buy five of each. For the other two types of stamps. I was asked to buy six of each. Unfortunately I forgot which I was supposed to buy five of and which to buy six of Luckily my mother had given me the exact money required to buy the stamps, Rs. 3.00 and the shopkeeper was able to give me the correct stamps. Which stamps did I buy?