Calculating the last/latest value in a GROUPBY function?

I've got some sales data, and I've mostly got it doing what I need, but there's one part I'm struggling with.

The (sample) sales data is:

(the total amount are cumulative, the 11:00:00 numbers include everything from the 10:00:00 sales, plus anything after up to 11:00:00 etc., and average value is just total amount / total items)

I'm using GROUPBY to get an end of day summary:

=GROUPBY(tblSalesAmounts[Date],tblSalesAmounts[[TotalAmount]:[TotalItems]],MAX,0,0,-1)

This works fine as it's the values at the end of the day I'm looking for, but I don't know how to add in the AverageValue - I can't get it via MAX as the average can change throughout the day, and it's last value of the day I'm after.

Any ideas on how to add in a latest/last value, in addition to the max's?