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	$192.83	3.590%	$199.7526	$199.75	$199.75	$199.80
Purchase #2	$145.85	3.447%	$150.8774	$150.88	$150.90	$150.90
Purchase #3	$221.91	11.517%	$247.4674	$247.47	$247.45	$247.50
Purchase #4	$100.81	13.471%	$114.3901	$114.39	$114.40	$114.40
Purchase #5	$128.36	8.725%	$139.5594	$139.56	$139.55	$139.60
Purchase #6	$80.82	13.379%	$91.6329	$91.63	$91.65	$91.60
Purchase #7	$172.79	10.259%	$190.5165	$190.52	$190.50	$190.50
7 purchase totals =	$1,043.37		$1,134.1963	$1,134.20	$1,134.20	$1,134.30