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	$51.59	5.603%	$54.4806	$54.48	$54.50	$54.50
Purchase #2	$145.30	5.334%	$153.0503	$153.05	$153.05	$153.10
Purchase #3	$146.63	10.184%	$161.5628	$161.56	$161.55	$161.60
Purchase #4	$142.35	10.552%	$157.3708	$157.37	$157.35	$157.40
Purchase #5	$136.95	10.295%	$151.049	$151.05	$151.05	$151.00
Purchase #6	$159.78	3.679%	$165.6583	$165.66	$165.65	$165.70
Purchase #7	$105.90	5.108%	$111.3094	$111.31	$111.30	$111.30
7 purchase totals =	$888.50		$954.4812	$954.48	$954.45	$954.60