acceptable range for pH buffers

We use +/- 0.5 for the acceptable range.

We use +/- 1 for our pH QC.

Our buffers had an acceptable range printed +/- 0.1

We use Ricca Chemical Company and they state the pH 5.00+/- 0.01 at 25C or =/-0.05 at all other temperatures. 

The original question mentions pHizatest.  The paper measures pH in the range of 4.5-7.5, and the color chart is in 0.5 increments.  You can't get a reading of "4.0" with a 4.0 buffer, because the paper doesn't read below 4.5.  We check this paper with 5.0 and 7.0 buffers.  We use +/- 0.5 because I was taught that an acceptable range is 1 increment to either side of the ideal pH.