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	$160.76	6.321%	$170.9216	$170.92	$170.90	$170.90
Purchase #2	$85.97	11.341%	$95.7199	$95.72	$95.70	$95.70
Purchase #3	$237.95	6.548%	$253.531	$253.53	$253.55	$253.50
Purchase #4	$45.57	4.687%	$47.7059	$47.71	$47.70	$47.70
Purchase #5	$235.31	8.751%	$255.902	$255.90	$255.90	$255.90
Purchase #6	$21.62	13.236%	$24.4816	$24.48	$24.50	$24.50
Purchase #7	$92.53	8.262%	$100.1748	$100.17	$100.15	$100.20
7 purchase totals =	$879.71		$948.4368	$948.43	$948.40	$948.40