Item entry in purchase/ sales invoice

I do two types of purchases and two type of sales. Purchases of TEA @1 % input vat and purchases of TEA @5% input vat . I have created two accounts under EXPENSES ACCOUNT, TEA PURCHASES @1% AND TEA PURCHASES @5%. MY problem is how to give entry in purchase invoice to get purchases of tea@1% seperately and purchases of tea@ 5% seperately and to get the monthly/yearly TOTAL of tea purchases made with stock book (inventory of purchases). IF I make the entries through purchase of inventory item account the item gets reflected in the inventory books but does not show the different type of purchases made . but if I make the entries through tea purchases@1% A/C or tea purchases@5% A/c created the inventory does NOT get reflected in the INVENTORY BOOKS.The same is for sales.I make two type of LOCAL SALES @5 %OUT PUT VAT and CST SALES @ 2% CST TAX.If the entries are made through SALES OF INVENTORY ITEM the sold item gets reflected in the INVENTORY BOOK. if the entry is made through the account created under INCOME for local sales@5% and cst sale @2% A/C the sold item does not get reflected in the stock book.I feel this is possible if the seperate accounts created is linked under purchases of inventory item or sale of inventory item or by linking item to a common inventory item account. request your valuable suggestions . This is important because the purchases are not made straight from the factory but through public tea auction through registered tea brokers to whom we make payment on behalf of the tea factory.