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	$51.91	9.522%	$56.8529	$56.85	$56.85	$56.90
Purchase #2	$157.98	11.802%	$176.6248	$176.62	$176.60	$176.60
Purchase #3	$89.82	6.363%	$95.5352	$95.54	$95.55	$95.50
Purchase #4	$156.87	12.854%	$177.0341	$177.03	$177.05	$177.00
Purchase #5	$208.66	4.695%	$218.4566	$218.46	$218.45	$218.50
Purchase #6	$186.55	9.265%	$203.8339	$203.83	$203.85	$203.80
Purchase #7	$99.82	5.353%	$105.1634	$105.16	$105.15	$105.20
7 purchase totals =	$951.61		$1,033.5009	$1,033.49	$1,033.50	$1,033.50