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	$142.90	7.429%	$153.516	$153.52	$153.50	$153.50
Purchase #2	$59.71	9.363%	$65.3006	$65.30	$65.30	$65.30
Purchase #3	$16.99	4.482%	$17.7515	$17.75	$17.75	$17.80
Purchase #4	$51.70	5.435%	$54.5099	$54.51	$54.50	$54.50
Purchase #5	$123.96	13.426%	$140.6029	$140.60	$140.60	$140.60
Purchase #6	$55.65	12.475%	$62.5923	$62.59	$62.60	$62.60
Purchase #7	$33.27	3.539%	$34.4474	$34.45	$34.45	$34.40
7 purchase totals =	$484.18		$528.7206	$528.72	$528.70	$528.70