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	$215.79	10.354%	$238.1329	$238.13	$238.15	$238.10
Purchase #2	$208.72	10.527%	$230.692	$230.69	$230.70	$230.70
Purchase #3	$191.60	4.163%	$199.5763	$199.58	$199.60	$199.60
Purchase #4	$49.62	4.576%	$51.8906	$51.89	$51.90	$51.90
Purchase #5	$185.52	3.328%	$191.6941	$191.69	$191.70	$191.70
Purchase #6	$128.73	3.456%	$133.1789	$133.18	$133.20	$133.20
Purchase #7	$146.58	6.125%	$155.558	$155.56	$155.55	$155.60
7 purchase totals =	$1,126.56		$1,200.7228	$1,200.72	$1,200.80	$1,200.80