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	$110.82	5.386%	$116.7888	$116.79	$116.80	$116.80
Purchase #2	$169.58	8.281%	$183.6229	$183.62	$183.60	$183.60
Purchase #3	$154.75	13.316%	$175.3565	$175.36	$175.35	$175.40
Purchase #4	$69.54	9.681%	$76.2722	$76.27	$76.25	$76.30
Purchase #5	$137.89	10.602%	$152.5091	$152.51	$152.50	$152.50
Purchase #6	$115.77	9.788%	$127.1016	$127.10	$127.10	$127.10
Purchase #7	$60.87	9.289%	$66.5242	$66.52	$66.50	$66.50
7 purchase totals =	$819.22		$898.1753	$898.17	$898.10	$898.20