The usual rate of duty on clothing imports from non-EU countries is 12%. (Some imports from the USA attract a rate of 27% but, to the best of my knowledge, this only applies to cotton-based goods. This is a UK trade sanction because the USA is in breach of World Trade Organization rules on subsidies to cotton producers). I'll assume that the 12% figure applies.
$189.95 is roughly �95. Since duty is charged on the value of the goods, I'll assume that your figure is made up of �80 ($160) for the boots and �15 ($30) for the carriage.
Based on those figures, Import Duty = 12% of �80 = approx �10.
VAT is charged, at 17.5%, on the boots, on the carriage and on the duty. (Yes, that is a tax on a tax!). So, VAT is 17.5% of �105 = approx �18.
Lastly, there's a customs examination fee of �8 to be paid.
So, based upon my rough figures, you can expect the postman to demand a total of around �36 before he'll hand over your package.
Chris