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	$68.42	5.476%	$72.1667	$72.17	$72.15	$72.20
Purchase #2	$105.60	12.209%	$118.4927	$118.49	$118.50	$118.50
Purchase #3	$138.97	5.605%	$146.7593	$146.76	$146.75	$146.80
Purchase #4	$80.25	11.641%	$89.5919	$89.59	$89.60	$89.60
Purchase #5	$18.45	3.192%	$19.0389	$19.04	$19.05	$19.00
Purchase #6	$140.48	4.746%	$147.1472	$147.15	$147.15	$147.10
Purchase #7	$102.27	10.246%	$112.7486	$112.75	$112.75	$112.70
7 purchase totals =	$654.44		$705.9453	$705.95	$705.95	$705.90