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	$79.62	4.711%	$83.3709	$83.37	$83.35	$83.40
Purchase #2	$141.49	9.654%	$155.1494	$155.15	$155.15	$155.10
Purchase #3	$108.29	5.302%	$114.0315	$114.03	$114.05	$114.00
Purchase #4	$205.89	4.493%	$215.1406	$215.14	$215.15	$215.10
Purchase #5	$249.57	13.260%	$282.663	$282.66	$282.65	$282.70
Purchase #6	$150.64	3.373%	$155.7211	$155.72	$155.70	$155.70
Purchase #7	$103.62	7.586%	$111.4806	$111.48	$111.50	$111.50
7 purchase totals =	$1,039.12		$1,117.5571	$1,117.55	$1,117.55	$1,117.50