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	$65.67	10.405%	$72.503	$72.50	$72.50	$72.50
Purchase #2	$140.75	7.292%	$151.0135	$151.01	$151.00	$151.00
Purchase #3	$14.37	10.475%	$15.8753	$15.88	$15.90	$15.90
Purchase #4	$48.75	3.386%	$50.4007	$50.40	$50.40	$50.40
Purchase #5	$126.35	6.591%	$134.6777	$134.68	$134.70	$134.70
Purchase #6	$103.55	13.780%	$117.8192	$117.82	$117.80	$117.80
Purchase #7	$75.87	8.293%	$82.1619	$82.16	$82.15	$82.20
7 purchase totals =	$575.31		$624.4513	$624.45	$624.45	$624.50