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	$155.54	9.189%	$169.8326	$169.83	$169.85	$169.80
Purchase #2	$62.87	12.401%	$70.6665	$70.67	$70.65	$70.70
Purchase #3	$183.37	6.371%	$195.0525	$195.05	$195.05	$195.10
Purchase #4	$113.67	3.826%	$118.019	$118.02	$118.00	$118.00
Purchase #5	$115.43	10.745%	$127.833	$127.83	$127.85	$127.80
Purchase #6	$99.86	5.837%	$105.6888	$105.69	$105.70	$105.70
Purchase #7	$95.52	4.491%	$99.8098	$99.81	$99.80	$99.80
7 purchase totals =	$826.26		$886.9022	$886.90	$886.90	$886.90