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	$222.85	7.773%	$240.1721	$240.17	$240.15	$240.20
Purchase #2	$249.49	12.462%	$280.5814	$280.58	$280.60	$280.60
Purchase #3	$223.74	12.465%	$251.6292	$251.63	$251.65	$251.60
Purchase #4	$217.85	13.768%	$247.8436	$247.84	$247.85	$247.80
Purchase #5	$103.33	8.173%	$111.7752	$111.78	$111.80	$111.80
Purchase #6	$48.90	6.519%	$52.0878	$52.09	$52.10	$52.10
Purchase #7	$52.82	6.106%	$56.0452	$56.05	$56.05	$56.00
7 purchase totals =	$1,118.98		$1,240.1345	$1,240.14	$1,240.20	$1,240.10