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	$96.55	6.286%	$102.6191	$102.62	$102.60	$102.60
Purchase #2	$71.61	3.107%	$73.8349	$73.83	$73.85	$73.80
Purchase #3	$227.51	7.504%	$244.5824	$244.58	$244.60	$244.60
Purchase #4	$83.35	8.200%	$90.1847	$90.18	$90.20	$90.20
Purchase #5	$189.71	10.548%	$209.7206	$209.72	$209.70	$209.70
Purchase #6	$108.50	5.148%	$114.0856	$114.09	$114.10	$114.10
Purchase #7	$106.27	7.786%	$114.5442	$114.54	$114.55	$114.50
7 purchase totals =	$883.50		$949.5715	$949.56	$949.60	$949.50