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	$29.37	11.429%	$32.7267	$32.73	$32.75	$32.70
Purchase #2	$21.84	3.820%	$22.6743	$22.67	$22.65	$22.70
Purchase #3	$70.89	13.602%	$80.5325	$80.53	$80.55	$80.50
Purchase #4	$40.40	11.748%	$45.1462	$45.15	$45.15	$45.10
Purchase #5	$106.97	10.851%	$118.5773	$118.58	$118.60	$118.60
Purchase #6	$110.83	4.869%	$116.2263	$116.23	$116.25	$116.20
Purchase #7	$63.78	10.462%	$70.4527	$70.45	$70.45	$70.50
7 purchase totals =	$444.08		$486.3360	$486.34	$486.40	$486.30