Information on call price rounding is within the General Notes part of the BT Price List.

http://www.bt.com/pricing/current/Gen_Notes_boo/0001_d0e219.htm#0001-d0e219


Quote:

Call Charge Rounding - Residential Customers - VAT Inclusive Billing (except for BT Basic customers) With some exceptions (see below), each call charge will be priced at VAT Exclusive rates and rounded up to a whole penny.  VAT will then be added, and the resulting price rounded up to a whole penny to determine the VAT Inclusive price.  Call charges to non-Mobile 07x numbers are subject to a Minimum Call Charge and will be priced at VAT Inclusive rates and rounded up to a tenth of a penny.  Any other types of call which have a Minimum Call Charge, and any call types which include a 'Pence per call' fee that buys a period of call time will be priced at VAT Inclusive rates and rounded up to a whole penny.  Fixed Fee prices where duration charges do not apply will be charged at the published VAT Inclusive price. The total call bill will be rounded to the nearest whole penny.

(It says "see below". I have done and I can't see where it lists the exceptions.)

I foolishly thought that for BT inclusive billing the price of the call inclusive of VAT was rounded up to the next whole penny. Perhaps it was and it has since quietly been changed again.

What happens now is that prices for each call, which are given on the bill inclusive of VAT, are calculated exclusive of VAT, rounded up to the next whole penny then VAT is added and rounded up to the next whole penny.

That is pretty outrageous, I didn't even think they were allowed to do that.