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	$143.93	7.754%	$155.0903	$155.09	$155.10	$155.10
Purchase #2	$192.45	4.301%	$200.7273	$200.73	$200.75	$200.70
Purchase #3	$30.48	9.106%	$33.2555	$33.26	$33.25	$33.30
Purchase #4	$166.64	12.551%	$187.555	$187.56	$187.55	$187.60
Purchase #5	$111.72	5.389%	$117.7406	$117.74	$117.75	$117.70
Purchase #6	$177.74	5.293%	$187.1478	$187.15	$187.15	$187.10
Purchase #7	$151.54	5.690%	$160.1626	$160.16	$160.15	$160.20
7 purchase totals =	$974.50		$1,041.6791	$1,041.69	$1,041.70	$1,041.70