In round(a,b), 'a' is the value to round and 'b' is the desired number of decimal places, i.e.:
round(4.17) = 4
round(4.17,0) = 4
round(4.17,1) = 4.2
round(4.17,9) = 4.17
round(a) is same as java.lang.Math.round(a), but I'm unclear if there's a sufficiently performant implementation for round(a,b). After a quick search, it looks like there are implementations involving Math.round with additional multiplication & division, and some involving DecimalFormat, NumberFormat, or BigDecimal. So not sure if round(a,b) is worthwhile.