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	$143.51	3.465%	$148.4826	$148.48	$148.50	$148.50
Purchase #2	$220.27	13.116%	$249.1606	$249.16	$249.15	$249.20
Purchase #3	$213.51	5.601%	$225.4687	$225.47	$225.45	$225.50
Purchase #4	$151.44	4.845%	$158.7773	$158.78	$158.80	$158.80
Purchase #5	$134.95	13.591%	$153.2911	$153.29	$153.30	$153.30
Purchase #6	$86.27	4.759%	$90.3756	$90.38	$90.40	$90.40
Purchase #7	$69.86	6.338%	$74.2877	$74.29	$74.30	$74.30
7 purchase totals =	$1,019.81		$1,099.8436	$1,099.85	$1,099.90	$1,100.00