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	$112.67	10.466%	$124.462	$124.46	$124.45	$124.50
Purchase #2	$10.27	11.653%	$11.4668	$11.47	$11.45	$11.50
Purchase #3	$181.59	5.268%	$191.1562	$191.16	$191.15	$191.20
Purchase #4	$17.99	4.368%	$18.7758	$18.78	$18.80	$18.80
Purchase #5	$85.27	12.500%	$95.9288	$95.93	$95.95	$95.90
Purchase #6	$32.70	10.790%	$36.2283	$36.23	$36.25	$36.20
Purchase #7	$173.40	7.848%	$187.0084	$187.01	$187.00	$187.00
7 purchase totals =	$613.89		$665.0263	$665.04	$665.05	$665.10