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	$192.60	12.426%	$216.5325	$216.53	$216.55	$216.50
Purchase #2	$154.26	4.188%	$160.7204	$160.72	$160.70	$160.70
Purchase #3	$188.61	10.736%	$208.8592	$208.86	$208.85	$208.90
Purchase #4	$51.78	5.785%	$54.7755	$54.78	$54.80	$54.80
Purchase #5	$216.38	5.158%	$227.5409	$227.54	$227.55	$227.50
Purchase #6	$14.62	6.531%	$15.5748	$15.57	$15.55	$15.60
Purchase #7	$145.42	3.443%	$150.4268	$150.43	$150.45	$150.40
7 purchase totals =	$963.67		$1,034.4301	$1,034.43	$1,034.45	$1,034.40