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	$67.89	8.512%	$73.6688	$73.67	$73.65	$73.70
Purchase #2	$146.86	6.456%	$156.3413	$156.34	$156.35	$156.30
Purchase #3	$208.81	6.650%	$222.6959	$222.70	$222.70	$222.70
Purchase #4	$5.43	13.312%	$6.1528	$6.15	$6.15	$6.20
Purchase #5	$48.67	3.248%	$50.2508	$50.25	$50.25	$50.30
Purchase #6	$49.27	8.786%	$53.5989	$53.60	$53.60	$53.60
Purchase #7	$112.51	9.449%	$123.1411	$123.14	$123.15	$123.10
7 purchase totals =	$639.44		$685.8496	$685.85	$685.85	$685.90