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	$48.46	4.773%	$50.773	$50.77	$50.75	$50.80
Purchase #2	$17.47	6.581%	$18.6197	$18.62	$18.60	$18.60
Purchase #3	$59.49	11.243%	$66.1785	$66.18	$66.20	$66.20
Purchase #4	$52.85	5.229%	$55.6135	$55.61	$55.60	$55.60
Purchase #5	$207.90	3.197%	$214.5466	$214.55	$214.55	$214.50
Purchase #6	$173.95	10.373%	$191.9938	$191.99	$192.00	$192.00
Purchase #7	$82.29	8.724%	$89.469	$89.47	$89.45	$89.50
7 purchase totals =	$642.41		$687.1941	$687.19	$687.15	$687.20