you cant trust steam for any information when it comes to tax, they have broken and are in lawsuits from around the around for misleading the government and people. 20% means it will always get a cut by that much, it will always be more than a £1. What you seeing on steam is incorrect price. This can be easy proven by math:
Anything lower than £1.03 with 20% VAT is £0.20 or less
£1.03 with 20% VAT is £0.21
Anything lower than £1.08 with 20% VAT is £0.21
£1.08 with 20% VAT is £0.22
Anything lower than £1.13 with 20% VAT is £0.22
£1.13 with 20% VAT is £0.23
Anything lower than £1.18 with 20% VAT is £0.23
£1.18 with 20% VAT is £0.24
Do you understand now, the numbers are always in prime numbers, every £0.05 makes VAT tax go by £0.01. Steam version of £0.97 is incorrect. They are breaking the law, Steam can not be trusted with anything.