Physical Science

The Vernier Scale 10 divisions of the Vernier scale have the same length as 9 divisions of the main scale
Simulator: Reading and interpretation of a milimetric (centimeterís tenth part) vernier scale (or nonius), practice with decimal precision (0.1mm)
Accuracy of Vernier Calipers Accuracy of a vernier caliper depends upon the least count of the vernier
Vernier Scales
How Does a Vernier Scale Work?
Using the vernier calipers and micrometer screw gauge
Significant Figures and Measuring Instruments
If a vernier mark coincides with a mark on the main scale, then the mark number is the fractional part of the main-scale division ... [and] ... a zero is added as the doubtful figure ... [otherwise] ... a suggested method is to take the middle of the digit [i.e. 5]
Significant figures no further digits after least division
De Anza College: The Vernier Scale this one says you can interpolate the last digit as 0 or 5