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	$182.27	8.792%	$198.2952	$198.30	$198.30	$198.30
Purchase #2	$59.56	6.724%	$63.5648	$63.56	$63.55	$63.60
Purchase #3	$225.79	3.562%	$233.8326	$233.83	$233.85	$233.80
Purchase #4	$20.90	5.244%	$21.996	$22.00	$22.00	$22.00
Purchase #5	$92.79	6.675%	$98.9837	$98.98	$99.00	$99.00
Purchase #6	$130.56	4.644%	$136.6232	$136.62	$136.60	$136.60
Purchase #7	$93.81	12.172%	$105.2286	$105.23	$105.25	$105.20
7 purchase totals =	$805.68		$858.5241	$858.52	$858.55	$858.50