VAT not included for additional participant fee when registering for events

Replication Steps
1) Create a event and set it to have multiple participant registration.
2) Setup a Financial type to have VAT and select this Financial type in the above created event
3) Register two participants for this event
2) Check the VAT on completing payment and check VAT amount in Invoice. (VAT amount shown is calculated for the total price for both cases)
4) Go to the contribution record and check the "Total Tax Amount"

Step 4 is where the issue is. The "Total Tax Amount" only counts the VAT for the first participant of the event.

For example:
If event fee is £10, and VAT is 20%. Then when registering 2 participants, the total fee is £20 and VAT should be £4. But the contribution record shows £2 for Total Tax Amount.