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	$179.74	4.146%	$187.192	$187.19	$187.20	$187.20
Purchase #2	$129.62	12.754%	$146.1517	$146.15	$146.15	$146.20
Purchase #3	$35.94	11.680%	$40.1378	$40.14	$40.15	$40.10
Purchase #4	$248.80	8.160%	$269.1021	$269.10	$269.10	$269.10
Purchase #5	$137.90	10.615%	$152.5381	$152.54	$152.55	$152.50
Purchase #6	$224.94	5.236%	$236.7179	$236.72	$236.70	$236.70
Purchase #7	$34.84	13.821%	$39.6552	$39.66	$39.65	$39.70
7 purchase totals =	$991.78		$1,071.4948	$1,071.50	$1,071.50	$1,071.50