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	$95.84	8.571%	$104.0544	$104.05	$104.05	$104.10
Purchase #2	$47.43	12.126%	$53.1814	$53.18	$53.20	$53.20
Purchase #3	$16.72	10.609%	$18.4938	$18.49	$18.50	$18.50
Purchase #4	$240.33	6.559%	$256.0932	$256.09	$256.10	$256.10
Purchase #5	$104.97	9.451%	$114.8907	$114.89	$114.90	$114.90
Purchase #6	$36.32	3.583%	$37.6213	$37.62	$37.60	$37.60
Purchase #7	$102.84	3.624%	$106.5669	$106.57	$106.55	$106.60
7 purchase totals =	$644.45		$690.9017	$690.89	$690.90	$691.00