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	$232.82	3.348%	$240.6148	$240.61	$240.60	$240.60
Purchase #2	$187.59	6.654%	$200.0722	$200.07	$200.05	$200.10
Purchase #3	$160.56	8.763%	$174.6299	$174.63	$174.65	$174.60
Purchase #4	$181.68	4.287%	$189.4686	$189.47	$189.45	$189.50
Purchase #5	$153.34	12.736%	$172.8694	$172.87	$172.85	$172.90
Purchase #6	$175.28	8.638%	$190.4207	$190.42	$190.40	$190.40
Purchase #7	$16.39	4.654%	$17.1528	$17.15	$17.15	$17.20
7 purchase totals =	$1,107.66		$1,185.2284	$1,185.22	$1,185.15	$1,185.30