Rounded Numbers are Cultural Attractors

Rounded numbers are cultural attractors: They are easier to remember and provide better symbols for magnitudes. So we celebrate twentieth wedding anniversaries, hundredth issues of journals, the millionth copy sold of a record, and so on. This, in turn, creates a special cultural attractor for prices, just below rounded numbers—$9.99 or $9,990 are likely price tags—so as to avoid the evocation of a higher magnitude.

 St. Augustine on Christian Explanations for Origins

It not infrequently happens that something about the earth, about the sky, about other elements of this world, about the motion and rotation or even the magnitude and distances of the stars, about definite eclipses of the sun and moon, about the passage of years and seasons, about the nature of animals, of fruits, of stones, and of other such things, may be known with the greatest certainty by reasoning or by experience, even by one who is not a Christian. It is too disgraceful and ruinous, t...