More correctly, round-half-to-even() can round to a multiple of 0.001, 0.01, 0.1, 1, 10, 100, 1000 etc.
Does it work to multiply by 4, round to a multiple of 100, then divide by 4?
Michael Kay
http://www.saxonica.com/
Author, XSLT 2.0 and XPath 2.0 Programmer's Reference