MultiCurrency Shipping Fee and CarrierService API

[otlit]

Hi Shopify Technical Support,

We are a Plus merchant. 

I am currently working on a way to charge shipping fee like below:

Destination	Currency	Shipping Fee
Hong Kong	HKD	HKD100 per order
Singapore	SGD	SGD30 per order
Taiwan	TWD	TWD750 per order

I used the Geolocation app to force TW customer to choose TWD and they can only choose Taiwan as delivery destination.  (My store default currency is HKD)

However, when it comes to shipping fee, even if I develop my own app using CarrierService API, it cannot do a exact TWD750 in shipping fee when checkout, instead it shows something like TWD761.62.

For instance, my app will return below in checkout:

{rates:{

    service_name: 'Standard Shipping',

    description: '',

    service_code: 'standard_shipping',

    currency: 'TWD',

    total_price: 75000

  }

 }

And the result is like:

Is there any way I can workaround?
Maybe anyway I can know how this 761.62 is calulated, so that I can adjust my code to deal with it?

Cheers,

Tom

Developer