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	$225.51	7.520%	$242.4684	$242.47	$242.45	$242.50
Purchase #2	$78.53	4.464%	$82.0356	$82.04	$82.05	$82.00
Purchase #3	$208.70	11.474%	$232.6462	$232.65	$232.65	$232.60
Purchase #4	$120.41	6.635%	$128.3992	$128.40	$128.40	$128.40
Purchase #5	$63.29	11.602%	$70.6329	$70.63	$70.65	$70.60
Purchase #6	$126.66	4.626%	$132.5193	$132.52	$132.50	$132.50
Purchase #7	$195.61	10.657%	$216.4562	$216.46	$216.45	$216.50
7 purchase totals =	$1,018.71		$1,105.1578	$1,105.17	$1,105.15	$1,105.10