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	$173.56	6.859%	$185.4645	$185.46	$185.45	$185.50
Purchase #2	$46.50	9.127%	$50.7441	$50.74	$50.75	$50.70
Purchase #3	$162.83	6.152%	$172.8473	$172.85	$172.85	$172.80
Purchase #4	$211.68	5.188%	$222.662	$222.66	$222.65	$222.70
Purchase #5	$7.85	3.397%	$8.1167	$8.12	$8.10	$8.10
Purchase #6	$139.36	10.370%	$153.8116	$153.81	$153.80	$153.80
Purchase #7	$101.26	5.613%	$106.9437	$106.94	$106.95	$106.90
7 purchase totals =	$843.04		$900.5899	$900.58	$900.55	$900.50