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	$106.74	3.204%	$110.1599	$110.16	$110.15	$110.20
Purchase #2	$59.72	13.644%	$67.8682	$67.87	$67.85	$67.90
Purchase #3	$96.58	12.818%	$108.9596	$108.96	$108.95	$109.00
Purchase #4	$70.76	4.247%	$73.7652	$73.77	$73.75	$73.80
Purchase #5	$58.43	5.346%	$61.5537	$61.55	$61.55	$61.60
Purchase #6	$100.81	10.377%	$111.2711	$111.27	$111.25	$111.30
Purchase #7	$243.79	4.135%	$253.8707	$253.87	$253.85	$253.90
7 purchase totals =	$736.83		$787.4484	$787.45	$787.35	$787.70