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	$14.76	4.679%	$15.4506	$15.45	$15.45	$15.50
Purchase #2	$110.61	12.153%	$124.0524	$124.05	$124.05	$124.10
Purchase #3	$176.82	11.339%	$196.8696	$196.87	$196.85	$196.90
Purchase #4	$111.82	4.198%	$116.5142	$116.51	$116.50	$116.50
Purchase #5	$222.49	10.184%	$245.1484	$245.15	$245.15	$245.10
Purchase #6	$215.79	11.585%	$240.7893	$240.79	$240.80	$240.80
Purchase #7	$144.52	3.219%	$149.1721	$149.17	$149.15	$149.20
7 purchase totals =	$996.81		$1,087.9966	$1,087.99	$1,087.95	$1,088.10