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	$113.99	11.365%	$126.945	$126.95	$126.95	$126.90
Purchase #2	$119.91	13.646%	$136.2729	$136.27	$136.25	$136.30
Purchase #3	$154.53	12.425%	$173.7304	$173.73	$173.75	$173.70
Purchase #4	$42.56	6.724%	$45.4217	$45.42	$45.40	$45.40
Purchase #5	$9.83	10.452%	$10.8574	$10.86	$10.85	$10.90
Purchase #6	$105.37	13.469%	$119.5623	$119.56	$119.55	$119.60
Purchase #7	$244.85	13.419%	$277.7064	$277.71	$277.70	$277.70
7 purchase totals =	$791.04		$890.4961	$890.50	$890.45	$890.50