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	$148.52	12.715%	$167.4043	$167.40	$167.40	$167.40
Purchase #2	$113.46	4.441%	$118.4988	$118.50	$118.50	$118.50
Purchase #3	$10.58	13.381%	$11.9957	$12.00	$12.00	$12.00
Purchase #4	$129.33	9.653%	$141.8142	$141.81	$141.80	$141.80
Purchase #5	$35.56	13.762%	$40.4538	$40.45	$40.45	$40.50
Purchase #6	$112.80	8.221%	$122.0733	$122.07	$122.05	$122.10
Purchase #7	$132.57	7.403%	$142.3842	$142.38	$142.40	$142.40
7 purchase totals =	$682.82		$744.6243	$744.61	$744.60	$744.70