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	$101.87	3.721%	$105.6606	$105.66	$105.65	$105.70
Purchase #2	$41.34	7.691%	$44.5195	$44.52	$44.50	$44.50
Purchase #3	$161.61	6.491%	$172.1001	$172.10	$172.10	$172.10
Purchase #4	$208.25	6.138%	$221.0324	$221.03	$221.05	$221.00
Purchase #5	$247.82	12.533%	$278.8793	$278.88	$278.90	$278.90
Purchase #6	$59.93	12.243%	$67.2672	$67.27	$67.25	$67.30
Purchase #7	$136.35	12.673%	$153.6296	$153.63	$153.65	$153.60
7 purchase totals =	$957.17		$1,043.0887	$1,043.09	$1,043.10	$1,043.10