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	$165.38	12.184%	$185.5299	$185.53	$185.55	$185.50
Purchase #2	$48.87	7.485%	$52.5279	$52.53	$52.55	$52.50
Purchase #3	$6.61	5.766%	$6.9911	$6.99	$7.00	$7.00
Purchase #4	$39.50	11.566%	$44.0686	$44.07	$44.05	$44.10
Purchase #5	$40.60	11.204%	$45.1488	$45.15	$45.15	$45.10
Purchase #6	$46.28	11.353%	$51.5342	$51.53	$51.55	$51.50
Purchase #7	$124.88	5.206%	$131.3813	$131.38	$131.40	$131.40
7 purchase totals =	$472.12		$517.1818	$517.18	$517.25	$517.10