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	$155.30	6.470%	$165.3479	$165.35	$165.35	$165.30
Purchase #2	$43.93	11.422%	$48.9477	$48.95	$48.95	$48.90
Purchase #3	$11.47	13.656%	$13.0363	$13.04	$13.05	$13.00
Purchase #4	$52.54	8.280%	$56.8903	$56.89	$56.90	$56.90
Purchase #5	$212.30	10.124%	$233.7933	$233.79	$233.80	$233.80
Purchase #6	$179.45	10.229%	$197.8059	$197.81	$197.80	$197.80
Purchase #7	$57.78	3.408%	$59.7491	$59.75	$59.75	$59.70
7 purchase totals =	$712.77		$775.5705	$775.58	$775.60	$775.40