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	$53.48	11.839%	$59.8115	$59.81	$59.80	$59.80
Purchase #2	$81.51	4.406%	$85.1013	$85.10	$85.10	$85.10
Purchase #3	$143.55	7.158%	$153.8253	$153.83	$153.85	$153.80
Purchase #4	$11.60	7.696%	$12.4927	$12.49	$12.50	$12.50
Purchase #5	$99.33	8.723%	$107.9946	$107.99	$108.00	$108.00
Purchase #6	$227.41	13.334%	$257.7328	$257.73	$257.75	$257.70
Purchase #7	$64.71	4.353%	$67.5268	$67.53	$67.55	$67.50
7 purchase totals =	$681.59		$744.4850	$744.48	$744.55	$744.40