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	$135.74	11.700%	$151.6216	$151.62	$151.60	$151.60
Purchase #2	$167.32	6.466%	$178.1389	$178.14	$178.15	$178.10
Purchase #3	$216.42	5.827%	$229.0308	$229.03	$229.05	$229.00
Purchase #4	$98.95	6.601%	$105.4817	$105.48	$105.50	$105.50
Purchase #5	$139.53	6.170%	$148.139	$148.14	$148.15	$148.10
Purchase #6	$226.58	8.451%	$245.7283	$245.73	$245.75	$245.70
Purchase #7	$88.54	13.106%	$100.1441	$100.14	$100.15	$100.10
7 purchase totals =	$1,073.08		$1,158.2844	$1,158.28	$1,158.35	$1,158.10