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	$216.49	6.331%	$230.196	$230.20	$230.20	$230.20
Purchase #2	$78.55	3.605%	$81.3817	$81.38	$81.40	$81.40
Purchase #3	$92.64	8.732%	$100.7293	$100.73	$100.75	$100.70
Purchase #4	$11.40	3.792%	$11.8323	$11.83	$11.85	$11.80
Purchase #5	$218.45	4.471%	$228.2169	$228.22	$228.20	$228.20
Purchase #6	$108.43	10.314%	$119.6135	$119.61	$119.60	$119.60
Purchase #7	$127.82	3.701%	$132.5506	$132.55	$132.55	$132.60
7 purchase totals =	$853.78		$904.5203	$904.52	$904.55	$904.50