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	$66.64	12.399%	$74.9027	$74.90	$74.90	$74.90
Purchase #2	$245.90	3.103%	$253.5303	$253.53	$253.55	$253.50
Purchase #3	$186.59	7.565%	$200.7055	$200.71	$200.70	$200.70
Purchase #4	$21.96	8.291%	$23.7807	$23.78	$23.80	$23.80
Purchase #5	$142.57	9.668%	$156.3537	$156.35	$156.35	$156.40
Purchase #6	$112.73	12.813%	$127.1741	$127.17	$127.15	$127.20
Purchase #7	$121.59	4.509%	$127.0725	$127.07	$127.05	$127.10
7 purchase totals =	$897.98		$963.5195	$963.51	$963.50	$963.60