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	$51.27	10.845%	$56.8302	$56.83	$56.85	$56.80
Purchase #2	$83.58	11.183%	$92.9268	$92.93	$92.95	$92.90
Purchase #3	$54.63	9.492%	$59.8155	$59.82	$59.80	$59.80
Purchase #4	$111.94	11.789%	$125.1366	$125.14	$125.15	$125.10
Purchase #5	$184.97	12.716%	$208.4908	$208.49	$208.50	$208.50
Purchase #6	$195.93	13.789%	$222.9468	$222.95	$222.95	$222.90
Purchase #7	$124.42	4.575%	$130.1122	$130.11	$130.10	$130.10
7 purchase totals =	$806.74		$896.2589	$896.27	$896.30	$896.10