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	$87.91	8.637%	$95.5028	$95.50	$95.50	$95.50
Purchase #2	$191.82	11.724%	$214.309	$214.31	$214.30	$214.30
Purchase #3	$188.72	10.671%	$208.8583	$208.86	$208.85	$208.90
Purchase #4	$38.47	4.616%	$40.2458	$40.25	$40.25	$40.20
Purchase #5	$17.81	3.509%	$18.435	$18.44	$18.45	$18.40
Purchase #6	$91.61	11.820%	$102.4383	$102.44	$102.45	$102.40
Purchase #7	$104.27	13.407%	$118.2495	$118.25	$118.25	$118.20
7 purchase totals =	$720.61		$798.0387	$798.05	$798.05	$797.90