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	$217.71	7.867%	$234.8372	$234.84	$234.85	$234.80
Purchase #2	$34.58	12.279%	$38.8261	$38.83	$38.85	$38.80
Purchase #3	$102.54	8.692%	$111.4528	$111.45	$111.45	$111.50
Purchase #4	$48.97	7.424%	$52.6055	$52.61	$52.60	$52.60
Purchase #5	$91.70	7.654%	$98.7187	$98.72	$98.70	$98.70
Purchase #6	$216.75	6.325%	$230.4594	$230.46	$230.45	$230.50
Purchase #7	$73.64	13.688%	$83.7198	$83.72	$83.70	$83.70
7 purchase totals =	$785.89		$850.6195	$850.63	$850.60	$850.60