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	$49.61	8.392%	$53.7733	$53.77	$53.75	$53.80
Purchase #2	$173.46	10.224%	$191.1946	$191.19	$191.20	$191.20
Purchase #3	$92.64	3.108%	$95.5193	$95.52	$95.50	$95.50
Purchase #4	$247.61	8.696%	$269.1422	$269.14	$269.15	$269.10
Purchase #5	$14.53	5.440%	$15.3204	$15.32	$15.30	$15.30
Purchase #6	$33.67	10.162%	$37.0915	$37.09	$37.10	$37.10
Purchase #7	$130.58	10.317%	$144.0519	$144.05	$144.05	$144.10
7 purchase totals =	$742.10		$806.0932	$806.08	$806.05	$806.10