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	$75.79	8.487%	$82.2223	$82.22	$82.20	$82.20
Purchase #2	$9.78	4.807%	$10.2501	$10.25	$10.25	$10.30
Purchase #3	$12.46	10.834%	$13.8099	$13.81	$13.80	$13.80
Purchase #4	$101.59	3.619%	$105.2665	$105.27	$105.25	$105.30
Purchase #5	$240.29	7.762%	$258.9413	$258.94	$258.95	$258.90
Purchase #6	$58.77	13.328%	$66.6029	$66.60	$66.60	$66.60
Purchase #7	$101.96	11.551%	$113.7374	$113.74	$113.75	$113.70
7 purchase totals =	$600.64		$650.8304	$650.83	$650.80	$650.80