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	$50.92	7.281%	$54.6275	$54.63	$54.65	$54.60
Purchase #2	$93.65	7.405%	$100.5848	$100.58	$100.60	$100.60
Purchase #3	$116.78	6.409%	$124.2644	$124.26	$124.25	$124.30
Purchase #4	$131.95	4.246%	$137.5526	$137.55	$137.55	$137.60
Purchase #5	$6.47	11.143%	$7.191	$7.19	$7.20	$7.20
Purchase #6	$46.85	10.632%	$51.8311	$51.83	$51.85	$51.80
Purchase #7	$135.91	11.579%	$151.647	$151.65	$151.65	$151.60
7 purchase totals =	$582.53		$627.6984	$627.69	$627.75	$627.70