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	$212.73	9.848%	$233.6797	$233.68	$233.70	$233.70
Purchase #2	$120.94	8.701%	$131.463	$131.46	$131.45	$131.50
Purchase #3	$240.71	9.451%	$263.4595	$263.46	$263.45	$263.50
Purchase #4	$40.66	4.714%	$42.5767	$42.58	$42.60	$42.60
Purchase #5	$97.81	6.557%	$104.2234	$104.22	$104.20	$104.20
Purchase #6	$234.55	3.519%	$242.8038	$242.80	$242.80	$242.80
Purchase #7	$48.39	10.717%	$53.576	$53.58	$53.60	$53.60
7 purchase totals =	$995.79		$1,071.7821	$1,071.78	$1,071.80	$1,071.90