Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$112.26	9.675%	$123.1212	$123.12	$123.10	$123.10
Purchase #2	$103.86	5.207%	$109.268	$109.27	$109.25	$109.30
Purchase #3	$120.57	3.493%	$124.7815	$124.78	$124.80	$124.80
Purchase #4	$142.72	6.537%	$152.0496	$152.05	$152.05	$152.00
Purchase #5	$79.46	5.553%	$83.8724	$83.87	$83.85	$83.90
Purchase #6	$114.51	13.870%	$130.3925	$130.39	$130.40	$130.40
Purchase #7	$16.51	13.583%	$18.7526	$18.75	$18.75	$18.80
7 purchase totals =	$689.89		$742.2378	$742.23	$742.20	$742.30