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	$149.32	4.361%	$155.8318	$155.83	$155.85	$155.80
Purchase #2	$52.43	8.818%	$57.0533	$57.05	$57.05	$57.10
Purchase #3	$247.40	11.515%	$275.8881	$275.89	$275.90	$275.90
Purchase #4	$222.81	6.848%	$238.068	$238.07	$238.05	$238.10
Purchase #5	$195.80	13.723%	$222.6696	$222.67	$222.65	$222.70
Purchase #6	$141.83	8.260%	$153.5452	$153.55	$153.55	$153.50
Purchase #7	$89.52	11.418%	$99.7414	$99.74	$99.75	$99.70
7 purchase totals =	$1,099.11		$1,202.7974	$1,202.80	$1,202.80	$1,202.80