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	$67.52	4.644%	$70.6556	$70.66	$70.65	$70.70
Purchase #2	$62.52	5.468%	$65.9386	$65.94	$65.95	$65.90
Purchase #3	$59.32	8.257%	$64.2181	$64.22	$64.20	$64.20
Purchase #4	$115.96	12.748%	$130.7426	$130.74	$130.75	$130.70
Purchase #5	$215.93	11.548%	$240.8656	$240.87	$240.85	$240.90
Purchase #6	$76.79	7.352%	$82.4356	$82.44	$82.45	$82.40
Purchase #7	$74.68	3.340%	$77.1743	$77.17	$77.15	$77.20
7 purchase totals =	$672.72		$732.0304	$732.04	$732.00	$732.00