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	$10.28	3.196%	$10.6085	$10.61	$10.60	$10.60
Purchase #2	$12.26	3.363%	$12.6723	$12.67	$12.65	$12.70
Purchase #3	$201.91	10.360%	$222.8279	$222.83	$222.85	$222.80
Purchase #4	$42.33	13.609%	$48.0907	$48.09	$48.10	$48.10
Purchase #5	$198.42	6.653%	$211.6209	$211.62	$211.60	$211.60
Purchase #6	$189.78	5.228%	$199.7017	$199.70	$199.70	$199.70
Purchase #7	$83.64	6.480%	$89.0599	$89.06	$89.05	$89.10
7 purchase totals =	$738.62		$794.5819	$794.58	$794.55	$794.60