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	$78.66	4.849%	$82.4742	$82.47	$82.45	$82.50
Purchase #2	$233.67	8.634%	$253.8451	$253.85	$253.85	$253.80
Purchase #3	$6.38	11.391%	$7.1067	$7.11	$7.10	$7.10
Purchase #4	$219.80	6.200%	$233.4276	$233.43	$233.45	$233.40
Purchase #5	$132.90	10.834%	$147.2984	$147.30	$147.30	$147.30
Purchase #6	$11.90	7.289%	$12.7674	$12.77	$12.75	$12.80
Purchase #7	$122.38	12.384%	$137.5355	$137.54	$137.55	$137.50
7 purchase totals =	$805.69		$874.4549	$874.47	$874.45	$874.40