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	$50.47	6.653%	$53.8278	$53.83	$53.85	$53.80
Purchase #2	$69.89	13.785%	$79.5243	$79.52	$79.50	$79.50
Purchase #3	$52.52	4.383%	$54.822	$54.82	$54.80	$54.80
Purchase #4	$160.55	13.839%	$182.7685	$182.77	$182.75	$182.80
Purchase #5	$63.25	13.382%	$71.7141	$71.71	$71.70	$71.70
Purchase #6	$199.29	6.455%	$212.1542	$212.15	$212.15	$212.20
Purchase #7	$43.52	5.850%	$46.0659	$46.07	$46.05	$46.10
7 purchase totals =	$639.49		$700.8768	$700.87	$700.80	$700.90