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	$112.95	9.188%	$123.3278	$123.33	$123.35	$123.30
Purchase #2	$69.35	13.496%	$78.7095	$78.71	$78.70	$78.70
Purchase #3	$106.77	12.337%	$119.9422	$119.94	$119.95	$119.90
Purchase #4	$177.61	5.596%	$187.5491	$187.55	$187.55	$187.50
Purchase #5	$33.50	3.406%	$34.641	$34.64	$34.65	$34.60
Purchase #6	$190.63	13.233%	$215.8561	$215.86	$215.85	$215.90
Purchase #7	$150.81	11.762%	$168.5483	$168.55	$168.55	$168.50
7 purchase totals =	$841.62		$928.5740	$928.58	$928.60	$928.40