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	$11.80	3.472%	$12.2097	$12.21	$12.20	$12.20
Purchase #2	$65.69	13.573%	$74.6061	$74.61	$74.60	$74.60
Purchase #3	$106.51	5.107%	$111.9495	$111.95	$111.95	$111.90
Purchase #4	$69.79	11.135%	$77.5611	$77.56	$77.55	$77.60
Purchase #5	$18.98	12.401%	$21.3337	$21.33	$21.35	$21.30
Purchase #6	$10.76	13.873%	$12.2527	$12.25	$12.25	$12.30
Purchase #7	$159.87	4.870%	$167.6557	$167.66	$167.65	$167.70
7 purchase totals =	$443.40		$477.5685	$477.57	$477.55	$477.60