Hi Yee
Please check the below link for your reference......
https://help.sap.com/saphelp_sbo900/helpdata/en/44/f8c616445241aae10000000a114a6b/content.htm
http://help.sap.com/saphelp_sbo900/helpdata/en/45/07dde4cc1a2462e10000000a1553f7/content.htm
How to Manage Landed Costs in SAP Business One - YouTube
http://www.tegrous.com/wp-content/uploads/2011/07/HowTo_Landed_Costs_2007A_B1.pdf
SAP Business One – Landed Costs, How do Customs Groups Work? | Clients First US Blog
Rgds,
Kamlesh Naware