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	$166.95	7.735%	$179.8636	$179.86	$179.85	$179.90
Purchase #2	$48.49	6.530%	$51.6564	$51.66	$51.65	$51.70
Purchase #3	$181.40	8.315%	$196.4834	$196.48	$196.50	$196.50
Purchase #4	$65.53	13.704%	$74.5102	$74.51	$74.50	$74.50
Purchase #5	$26.76	10.145%	$29.4748	$29.47	$29.45	$29.50
Purchase #6	$118.89	8.111%	$128.5332	$128.53	$128.55	$128.50
Purchase #7	$194.50	8.113%	$210.2798	$210.28	$210.30	$210.30
7 purchase totals =	$802.52		$870.8014	$870.79	$870.80	$870.90