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	$29.40	10.293%	$32.4261	$32.43	$32.45	$32.40
Purchase #2	$21.68	9.690%	$23.7808	$23.78	$23.80	$23.80
Purchase #3	$16.51	12.633%	$18.5957	$18.60	$18.60	$18.60
Purchase #4	$68.64	13.865%	$78.1569	$78.16	$78.15	$78.20
Purchase #5	$141.25	11.537%	$157.546	$157.55	$157.55	$157.50
Purchase #6	$12.25	6.553%	$13.0527	$13.05	$13.05	$13.10
Purchase #7	$80.45	3.741%	$83.4596	$83.46	$83.45	$83.50
7 purchase totals =	$370.18		$407.0178	$407.03	$407.05	$407.10