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	$98.72	6.838%	$105.4705	$105.47	$105.45	$105.50
Purchase #2	$234.85	9.332%	$256.7662	$256.77	$256.75	$256.80
Purchase #3	$19.71	6.656%	$21.0219	$21.02	$21.00	$21.00
Purchase #4	$199.58	12.121%	$223.7711	$223.77	$223.75	$223.80
Purchase #5	$93.83	7.252%	$100.6346	$100.63	$100.65	$100.60
Purchase #6	$120.75	9.845%	$132.6378	$132.64	$132.65	$132.60
Purchase #7	$119.58	3.143%	$123.3384	$123.34	$123.35	$123.30
7 purchase totals =	$887.02		$963.6405	$963.64	$963.60	$963.60