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	$211.62	9.318%	$231.3388	$231.34	$231.35	$231.30
Purchase #2	$213.81	9.161%	$233.3971	$233.40	$233.40	$233.40
Purchase #3	$190.26	5.526%	$200.7738	$200.77	$200.75	$200.80
Purchase #4	$58.37	13.313%	$66.1408	$66.14	$66.15	$66.10
Purchase #5	$70.83	10.725%	$78.4265	$78.43	$78.45	$78.40
Purchase #6	$178.29	6.856%	$190.5136	$190.51	$190.50	$190.50
Purchase #7	$207.96	12.722%	$234.4167	$234.42	$234.40	$234.40
7 purchase totals =	$1,131.14		$1,235.0073	$1,235.01	$1,235.00	$1,234.90