Improve accuracy at checkout with a cannabis POS for Massachusetts dispensaries that validates product eligibility

https://wiki-byte.win/index.php/Metrc-Compliant_POS_for_Massachusetts:_Mapping_METRC_Data_to_POS_Transactions

Improve accuracy at checkout with a cannabis POS for Massachusetts dispensaries that validates product eligibility, calculates totals successfully, and supports a couple of cost types.