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	$45.42	6.403%	$48.3282	$48.33	$48.35	$48.30
Purchase #2	$60.97	10.690%	$67.4877	$67.49	$67.50	$67.50
Purchase #3	$155.91	7.523%	$167.6391	$167.64	$167.65	$167.60
Purchase #4	$225.75	8.749%	$245.5009	$245.50	$245.50	$245.50
Purchase #5	$45.93	5.638%	$48.5195	$48.52	$48.50	$48.50
Purchase #6	$119.27	7.443%	$128.1473	$128.15	$128.15	$128.10
Purchase #7	$143.32	9.147%	$156.4295	$156.43	$156.45	$156.40
7 purchase totals =	$796.57		$862.0522	$862.06	$862.10	$861.90