Use this function to calculate the value of tax (gst, vat) for a given amount.

The amount can include or exclude the tax amount, and the ex-tax amount is returned as well.

You can round the tax amount by specifying a rounding value, for example, to round to the nearest 5 cents pass 5 as the rounding value.

::Example::

amount = 11000 ;* dollar value of the amount to calculate the tax on, in cents (MD2)
type = "I" ;* does the amount include or exclude the tax (I for include, E for exclude)
taxRate = "10%" ;* the tax rate, can be passed as 10% or 10 or 0.01
rounding = 5 ;* round the tax amount to the nearest 5 cents.

taxAmount = rgd_calculate_GST(amount,type,taxRate,rounding,exTaxAmount)

* taxAmount will be set to 1000 (in cents MD2)
* exTaxAmount will be set to 10000 (in cents MD2)

source code attached below.