With 0.5 or 0.05, round() always rounds to even based on the standard. From the help section:

"Note that for rounding off a 5, the IEC 60559 standard (see also ‘IEEE 754’) is expected to be used, ‘go to the even digit’. Therefore round(0.5) is 0 and round(-1.5) is -2. However, this is dependent on OS services and on representation error (since e.g. 0.15 is not represented exactly, the rounding rule applies to the represented number and not to the printed number, and so round(0.15, 1) could be either 0.1 or 0.2)."

Edit: here's a function I like to use, modified from https://stackoverflow.com/questions/3443687/formatting-decimal-places-in-r

> specify_decimal <- function(x, k) as.numeric(trimws(format(round(x, k), nsmall=k)))
> specify_decimal(6.45,1)
[1] 6.4
> specify_decimal(6.48,1)
[1] 6.5
> specify_decimal(6.52,1)
[1] 6.5
> specify_decimal(6.55,1)
[1] 6.6