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	$158.36	13.546%	$179.8114	$179.81	$179.80	$179.80
Purchase #2	$91.62	5.574%	$96.7269	$96.73	$96.75	$96.70
Purchase #3	$49.49	9.388%	$54.1361	$54.14	$54.15	$54.10
Purchase #4	$226.94	12.205%	$254.638	$254.64	$254.65	$254.60
Purchase #5	$150.61	5.314%	$158.6134	$158.61	$158.60	$158.60
Purchase #6	$184.82	7.788%	$199.2138	$199.21	$199.20	$199.20
Purchase #7	$40.70	4.627%	$42.5832	$42.58	$42.60	$42.60
7 purchase totals =	$902.54		$985.7228	$985.72	$985.75	$985.60