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	$128.78	9.493%	$141.0051	$141.01	$141.00	$141.00
Purchase #2	$72.81	10.664%	$80.5745	$80.57	$80.55	$80.60
Purchase #3	$120.85	3.794%	$125.435	$125.44	$125.45	$125.40
Purchase #4	$93.38	7.755%	$100.6216	$100.62	$100.60	$100.60
Purchase #5	$12.73	7.117%	$13.636	$13.64	$13.65	$13.60
Purchase #6	$77.88	13.348%	$88.2754	$88.28	$88.30	$88.30
Purchase #7	$185.38	7.504%	$199.2909	$199.29	$199.30	$199.30
7 purchase totals =	$691.81		$748.8385	$748.85	$748.85	$748.80