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	$42.38	5.832%	$44.8516	$44.85	$44.85	$44.90
Purchase #2	$239.91	6.603%	$255.7513	$255.75	$255.75	$255.80
Purchase #3	$126.47	11.413%	$140.904	$140.90	$140.90	$140.90
Purchase #4	$74.47	13.160%	$84.2703	$84.27	$84.25	$84.30
Purchase #5	$57.52	3.214%	$59.3687	$59.37	$59.35	$59.40
Purchase #6	$174.27	3.178%	$179.8083	$179.81	$179.80	$179.80
Purchase #7	$137.27	12.194%	$154.0087	$154.01	$154.00	$154.00
7 purchase totals =	$852.29		$918.9629	$918.96	$918.90	$919.10