Rounding in RTF Template Formula

Dear All,

I am attempting to round the total of X/Y numbers in a sum, but it's not working using the RTF template. This is my formula:

<?sum(current-group()/TOTAL_PREST)?>

I need to round this equation (current-group()/TOTAL_PREST) to the nearest hundredth in the following manner:

If current-group()/TOTAL_PREST = 7.878, it should be equal to 7.88
If current-group()/TOTAL_PREST = 7.874, it should be equal to 7.88

I am using this tag, but it's not working: <?xdofx:sum(round(current-group()/TOTAL_PREST, 2))?>

Can anyone provide any help? It will be very appreciated.

Thank you in advance,