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	$12.55	7.346%	$13.4719	$13.47	$13.45	$13.50
Purchase #2	$60.50	5.720%	$63.9606	$63.96	$63.95	$64.00
Purchase #3	$123.35	4.457%	$128.8477	$128.85	$128.85	$128.80
Purchase #4	$165.60	4.840%	$173.615	$173.62	$173.60	$173.60
Purchase #5	$107.93	3.202%	$111.3859	$111.39	$111.40	$111.40
Purchase #6	$189.84	13.443%	$215.3602	$215.36	$215.35	$215.40
Purchase #7	$113.60	6.441%	$120.917	$120.92	$120.90	$120.90
7 purchase totals =	$773.37		$827.5583	$827.57	$827.50	$827.60