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	$104.65	4.320%	$109.1709	$109.17	$109.15	$109.20
Purchase #2	$179.87	6.163%	$190.9554	$190.96	$190.95	$191.00
Purchase #3	$10.25	6.723%	$10.9391	$10.94	$10.95	$10.90
Purchase #4	$56.57	4.773%	$59.2701	$59.27	$59.25	$59.30
Purchase #5	$112.56	11.565%	$125.5776	$125.58	$125.60	$125.60
Purchase #6	$137.94	4.382%	$143.9845	$143.98	$144.00	$144.00
Purchase #7	$107.58	10.437%	$118.8081	$118.81	$118.80	$118.80
7 purchase totals =	$709.42		$758.7057	$758.71	$758.70	$758.80