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	$97.36	7.676%	$104.8334	$104.83	$104.85	$104.80
Purchase #2	$74.91	13.772%	$85.2266	$85.23	$85.25	$85.20
Purchase #3	$130.77	10.102%	$143.9804	$143.98	$144.00	$144.00
Purchase #4	$182.47	4.485%	$190.6538	$190.65	$190.65	$190.70
Purchase #5	$53.47	10.690%	$59.1859	$59.19	$59.20	$59.20
Purchase #6	$125.80	4.395%	$131.3289	$131.33	$131.35	$131.30
Purchase #7	$157.42	7.826%	$169.7397	$169.74	$169.75	$169.70
7 purchase totals =	$822.20		$884.9487	$884.95	$885.05	$884.90