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	$83.54	7.248%	$89.595	$89.60	$89.60	$89.60
Purchase #2	$247.33	4.336%	$258.0542	$258.05	$258.05	$258.10
Purchase #3	$226.81	12.481%	$255.1182	$255.12	$255.10	$255.10
Purchase #4	$76.49	10.439%	$84.4748	$84.47	$84.45	$84.50
Purchase #5	$64.66	12.643%	$72.835	$72.84	$72.85	$72.80
Purchase #6	$110.72	5.507%	$116.8174	$116.82	$116.80	$116.80
Purchase #7	$214.70	6.405%	$228.4515	$228.45	$228.45	$228.50
7 purchase totals =	$1,024.25		$1,105.3461	$1,105.35	$1,105.30	$1,105.40