If we have a column of times we're adding up in a formula like, say,
=sum(C4:C20) and we're dealing with times is there a way to modify
that formula so that it rounds the total to the nearest quarter hour?

p.s., since the spreadsheet had to take into account "negative" hours
in terms of subtracting hours, the spreadsheet is set to the 1904
system. Don't know if that makes any difference to the above.

Tx.