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	$61.49	10.181%	$67.7503	$67.75	$67.75	$67.80
Purchase #2	$52.59	3.480%	$54.4201	$54.42	$54.40	$54.40
Purchase #3	$47.65	10.248%	$52.5332	$52.53	$52.55	$52.50
Purchase #4	$64.28	11.160%	$71.4536	$71.45	$71.45	$71.50
Purchase #5	$56.81	12.754%	$64.0555	$64.06	$64.05	$64.10
Purchase #6	$115.75	10.823%	$128.2776	$128.28	$128.30	$128.30
Purchase #7	$43.48	6.509%	$46.3101	$46.31	$46.30	$46.30
7 purchase totals =	$442.05		$484.8004	$484.80	$484.80	$484.90