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	$173.61	10.184%	$191.2904	$191.29	$191.30	$191.30
Purchase #2	$47.52	5.357%	$50.0656	$50.07	$50.05	$50.10
Purchase #3	$42.81	8.528%	$46.4608	$46.46	$46.45	$46.50
Purchase #4	$222.43	7.452%	$239.0055	$239.01	$239.00	$239.00
Purchase #5	$217.47	5.216%	$228.8132	$228.81	$228.80	$228.80
Purchase #6	$221.86	12.493%	$249.577	$249.58	$249.60	$249.60
Purchase #7	$81.79	11.523%	$91.2147	$91.21	$91.20	$91.20
7 purchase totals =	$1,007.49		$1,096.4272	$1,096.43	$1,096.40	$1,096.50