A check is being mailed to pay taxes on a property in a distant city. Bank wants to charge borrower the fee for sending this check UPS, where is this courier fee itemized on the GFE and HUD?

It would be part of the origination fee.

HUD-1 – General
1) Q: How are courier and overnight delivery fees shown on the HUD-1 Settlement Statement?

A: Courier and overnight delivery fees are considered to be fees for administrative or processing services. They are part of a primary service, such as the origination service or title service, and may not be separately itemized.

So it should be included as part of the origination fee on both the GFE and HUD?

Yes.

So...can we only charge the borrower the EXACT cost of the courier fee since it is disclosed in Block 1 of the GFE? Or if it cost $10.53 and we know that, can we still charge the $15 that we disclosed in the GFE?

I would suggest you read the lastest court rulings on fee-splitting and then make your decision.