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	$207.44	12.226%	$232.8016	$232.80	$232.80	$232.80
Purchase #2	$172.89	3.140%	$178.3187	$178.32	$178.30	$178.30
Purchase #3	$240.47	6.797%	$256.8147	$256.81	$256.80	$256.80
Purchase #4	$132.76	8.710%	$144.3234	$144.32	$144.30	$144.30
Purchase #5	$74.42	8.438%	$80.6996	$80.70	$80.70	$80.70
Purchase #6	$53.63	11.201%	$59.6371	$59.64	$59.65	$59.60
Purchase #7	$93.82	10.189%	$103.3793	$103.38	$103.40	$103.40
7 purchase totals =	$975.43		$1,055.9744	$1,055.97	$1,055.95	$1,055.90