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	$233.29	9.798%	$256.1478	$256.15	$256.15	$256.10
Purchase #2	$18.73	13.148%	$21.1926	$21.19	$21.20	$21.20
Purchase #3	$39.75	5.193%	$41.8142	$41.81	$41.80	$41.80
Purchase #4	$169.86	6.366%	$180.6733	$180.67	$180.65	$180.70
Purchase #5	$59.46	6.827%	$63.5193	$63.52	$63.50	$63.50
Purchase #6	$90.54	3.634%	$93.8302	$93.83	$93.85	$93.80
Purchase #7	$121.89	4.864%	$127.8187	$127.82	$127.80	$127.80
7 purchase totals =	$733.52		$784.9961	$784.99	$784.95	$784.90