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	$54.79	9.248%	$59.857	$59.86	$59.85	$59.90
Purchase #2	$59.55	13.336%	$67.4916	$67.49	$67.50	$67.50
Purchase #3	$113.37	11.862%	$126.8179	$126.82	$126.80	$126.80
Purchase #4	$18.81	8.686%	$20.4438	$20.44	$20.45	$20.40
Purchase #5	$151.87	12.622%	$171.039	$171.04	$171.05	$171.00
Purchase #6	$44.70	3.847%	$46.4196	$46.42	$46.40	$46.40
Purchase #7	$110.58	3.682%	$114.6516	$114.65	$114.65	$114.70
7 purchase totals =	$553.67		$606.7205	$606.72	$606.70	$606.70