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	$46.70	3.569%	$48.3667	$48.37	$48.35	$48.40
Purchase #2	$88.61	8.615%	$96.2438	$96.24	$96.25	$96.20
Purchase #3	$52.42	4.411%	$54.7322	$54.73	$54.75	$54.70
Purchase #4	$72.45	5.662%	$76.5521	$76.55	$76.55	$76.60
Purchase #5	$51.96	12.189%	$58.2934	$58.29	$58.30	$58.30
Purchase #6	$208.90	6.496%	$222.4701	$222.47	$222.45	$222.50
Purchase #7	$11.43	12.395%	$12.8467	$12.85	$12.85	$12.80
7 purchase totals =	$532.47		$569.5050	$569.50	$569.50	$569.50