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	$37.77	7.768%	$40.704	$40.70	$40.70	$40.70
Purchase #2	$46.55	3.766%	$48.3031	$48.30	$48.30	$48.30
Purchase #3	$170.57	3.437%	$176.4325	$176.43	$176.45	$176.40
Purchase #4	$228.79	12.175%	$256.6452	$256.65	$256.65	$256.60
Purchase #5	$173.84	13.183%	$196.7573	$196.76	$196.75	$196.80
Purchase #6	$217.74	13.689%	$247.5464	$247.55	$247.55	$247.50
Purchase #7	$99.58	3.706%	$103.2704	$103.27	$103.25	$103.30
7 purchase totals =	$974.84		$1,069.6589	$1,069.66	$1,069.65	$1,069.60