Hi, Beerman, if you read what's below then look at your bill it should make sense.

The TGCA is a tax applicable on the entire territory of the Community of St. Martin in the French West Indies since August 1, 2010. It is due to local economic operations , including sales and services. Are involved all stakeholders in the economy of the island, businesses, commerce and the professions. The amount of 4% on sales is donated to the Community in order to enable it to increase the budget and finances. It is always charged . Are exempt import of goods , sales of prescription drugs, bread, water supply, and the goods when exported from the island except on the Dutch side that remains taxable.

4% of the Montant HT 36.54 is 1.46; the two added together totals 38.00 Euros.

The exchange rate from Euros to dollars is another thing. Could be what BeachKitten suggested, the merchant charging what they want for the exchange rate.

I have found that if I use US dollars (cash) to buy anything in Marigot the vendors usually want a few more dollars.