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	$59.51	3.585%	$61.6434	$61.64	$61.65	$61.60
Purchase #2	$50.72	11.313%	$56.458	$56.46	$56.45	$56.50
Purchase #3	$83.45	13.625%	$94.8201	$94.82	$94.80	$94.80
Purchase #4	$113.28	13.507%	$128.5807	$128.58	$128.60	$128.60
Purchase #5	$180.31	7.645%	$194.0947	$194.09	$194.10	$194.10
Purchase #6	$20.30	12.165%	$22.7695	$22.77	$22.75	$22.80
Purchase #7	$100.51	6.530%	$107.0733	$107.07	$107.05	$107.10
7 purchase totals =	$608.08		$665.4397	$665.43	$665.40	$665.50