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	$108.85	6.522%	$115.9492	$115.95	$115.95	$115.90
Purchase #2	$93.77	13.590%	$106.5133	$106.51	$106.50	$106.50
Purchase #3	$95.60	5.223%	$100.5932	$100.59	$100.60	$100.60
Purchase #4	$131.63	13.361%	$149.2171	$149.22	$149.20	$149.20
Purchase #5	$78.93	13.783%	$89.8089	$89.81	$89.80	$89.80
Purchase #6	$100.74	10.719%	$111.5383	$111.54	$111.55	$111.50
Purchase #7	$190.49	11.680%	$212.7392	$212.74	$212.75	$212.70
7 purchase totals =	$800.01		$886.3592	$886.36	$886.35	$886.20