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	$173.96	12.701%	$196.0547	$196.05	$196.05	$196.10
Purchase #2	$174.78	12.286%	$196.2535	$196.25	$196.25	$196.30
Purchase #3	$199.93	11.362%	$222.646	$222.65	$222.65	$222.60
Purchase #4	$222.57	3.702%	$230.8095	$230.81	$230.80	$230.80
Purchase #5	$43.33	8.336%	$46.942	$46.94	$46.95	$46.90
Purchase #6	$30.99	4.431%	$32.3632	$32.36	$32.35	$32.40
Purchase #7	$52.47	8.309%	$56.8297	$56.83	$56.85	$56.80
7 purchase totals =	$898.03		$981.8986	$981.89	$981.90	$981.90