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	$10.26	11.598%	$11.45	$11.45	$11.45	$11.50
Purchase #2	$24.39	6.365%	$25.9424	$25.94	$25.95	$25.90
Purchase #3	$177.42	4.195%	$184.8628	$184.86	$184.85	$184.90
Purchase #4	$39.85	6.600%	$42.4801	$42.48	$42.50	$42.50
Purchase #5	$47.85	12.599%	$53.8786	$53.88	$53.90	$53.90
Purchase #6	$136.92	7.285%	$146.8946	$146.89	$146.90	$146.90
Purchase #7	$43.79	11.289%	$48.7335	$48.73	$48.75	$48.70
7 purchase totals =	$480.48		$514.2420	$514.23	$514.30	$514.30