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	$60.40	10.242%	$66.5862	$66.59	$66.60	$66.60
Purchase #2	$133.98	6.704%	$142.962	$142.96	$142.95	$143.00
Purchase #3	$173.72	8.547%	$188.5678	$188.57	$188.55	$188.60
Purchase #4	$32.26	13.806%	$36.7138	$36.71	$36.70	$36.70
Purchase #5	$246.72	11.661%	$275.49	$275.49	$275.50	$275.50
Purchase #6	$138.71	5.121%	$145.8133	$145.81	$145.80	$145.80
Purchase #7	$37.27	11.327%	$41.4916	$41.49	$41.50	$41.50
7 purchase totals =	$823.06		$897.6247	$897.62	$897.60	$897.70