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	$62.99	8.677%	$68.4556	$68.46	$68.45	$68.50
Purchase #2	$121.61	9.470%	$133.1265	$133.13	$133.15	$133.10
Purchase #3	$44.29	5.719%	$46.8229	$46.82	$46.80	$46.80
Purchase #4	$100.54	10.858%	$111.4566	$111.46	$111.45	$111.50
Purchase #5	$214.97	8.784%	$233.853	$233.85	$233.85	$233.90
Purchase #6	$94.83	5.155%	$99.7185	$99.72	$99.70	$99.70
Purchase #7	$231.99	5.639%	$245.0719	$245.07	$245.05	$245.10
7 purchase totals =	$871.22		$938.5050	$938.51	$938.45	$938.60