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	$49.82	6.679%	$53.1475	$53.15	$53.15	$53.10
Purchase #2	$19.38	13.137%	$21.926	$21.93	$21.95	$21.90
Purchase #3	$99.83	3.246%	$103.0705	$103.07	$103.05	$103.10
Purchase #4	$87.35	3.310%	$90.2413	$90.24	$90.25	$90.20
Purchase #5	$8.71	11.638%	$9.7237	$9.72	$9.70	$9.70
Purchase #6	$245.61	10.817%	$272.1776	$272.18	$272.20	$272.20
Purchase #7	$156.77	6.549%	$167.0369	$167.04	$167.05	$167.00
7 purchase totals =	$667.47		$717.3235	$717.33	$717.35	$717.20