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	$163.68	8.245%	$177.1754	$177.18	$177.20	$177.20
Purchase #2	$141.37	6.641%	$150.7584	$150.76	$150.75	$150.80
Purchase #3	$114.83	11.218%	$127.7116	$127.71	$127.70	$127.70
Purchase #4	$148.58	13.763%	$169.0291	$169.03	$169.05	$169.00
Purchase #5	$175.28	8.435%	$190.0649	$190.06	$190.05	$190.10
Purchase #6	$102.67	8.702%	$111.6043	$111.60	$111.60	$111.60
Purchase #7	$152.67	11.488%	$170.2087	$170.21	$170.20	$170.20
7 purchase totals =	$999.08		$1,096.5524	$1,096.55	$1,096.55	$1,096.60