Is there a log of all the API calls triggered?

Thank you for this information, so if someone adds to my shopping car 2 products one costing: 7,20 GBP and the other one costing 8 GBP, the total for the client to pay would be: 15,20 so to charge 15,20 GBP its not possible, therefore I have to charge only 15 GBP?. Thanks.