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	$146.29	4.571%	$152.9769	$152.98	$153.00	$153.00
Purchase #2	$98.76	13.291%	$111.8862	$111.89	$111.90	$111.90
Purchase #3	$175.74	5.173%	$184.831	$184.83	$184.85	$184.80
Purchase #4	$93.75	10.437%	$103.5347	$103.53	$103.55	$103.50
Purchase #5	$45.27	10.845%	$50.1795	$50.18	$50.20	$50.20
Purchase #6	$249.42	3.504%	$258.1597	$258.16	$258.15	$258.20
Purchase #7	$19.71	8.776%	$21.4397	$21.44	$21.45	$21.40
7 purchase totals =	$828.94		$883.0077	$883.01	$883.10	$883.00