Rounding

Any hard fast rules on rounding? I had a mock situation where I rounded the SD in Domestic dollars from .35XX to .36 and my contribution of the currency was off the guildline answer by a few basis points, not a problem if its multiple choice but I don’t know how they might handle it on the AM part of exam.

Also when doing corner Corner portfolios I did them to 4 decimal places and the weights of the underlying assets were off slightly as compared to the guidline answers. Any ideas? I’d hate to lose marks due to rounding.