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	$177.61	4.340%	$185.3183	$185.32	$185.30	$185.30
Purchase #2	$56.75	13.224%	$64.2546	$64.25	$64.25	$64.30
Purchase #3	$18.93	11.174%	$21.0452	$21.05	$21.05	$21.00
Purchase #4	$203.29	10.801%	$225.2474	$225.25	$225.25	$225.20
Purchase #5	$33.32	3.175%	$34.3779	$34.38	$34.40	$34.40
Purchase #6	$238.95	7.687%	$257.3181	$257.32	$257.30	$257.30
Purchase #7	$13.52	9.702%	$14.8317	$14.83	$14.85	$14.80
7 purchase totals =	$742.37		$802.3932	$802.40	$802.40	$802.30