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	$218.67	7.422%	$234.8997	$234.90	$234.90	$234.90
Purchase #2	$47.81	6.300%	$50.822	$50.82	$50.80	$50.80
Purchase #3	$158.65	11.310%	$176.5933	$176.59	$176.60	$176.60
Purchase #4	$168.53	10.262%	$185.8245	$185.82	$185.80	$185.80
Purchase #5	$114.97	10.598%	$127.1545	$127.15	$127.15	$127.20
Purchase #6	$224.98	6.493%	$239.588	$239.59	$239.60	$239.60
Purchase #7	$160.81	4.576%	$168.1687	$168.17	$168.15	$168.20
7 purchase totals =	$1,094.42		$1,183.0507	$1,183.04	$1,183.00	$1,183.10