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	$62.61	12.516%	$70.4463	$70.45	$70.45	$70.40
Purchase #2	$73.30	6.857%	$78.3262	$78.33	$78.35	$78.30
Purchase #3	$247.80	11.326%	$275.8658	$275.87	$275.85	$275.90
Purchase #4	$13.27	3.501%	$13.7346	$13.73	$13.75	$13.70
Purchase #5	$173.34	12.684%	$195.3264	$195.33	$195.35	$195.30
Purchase #6	$76.90	6.705%	$82.0561	$82.06	$82.05	$82.10
Purchase #7	$228.52	10.676%	$252.9168	$252.92	$252.90	$252.90
7 purchase totals =	$875.74		$968.6722	$968.69	$968.70	$968.60