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	$112.89	3.224%	$116.5296	$116.53	$116.55	$116.50
Purchase #2	$119.91	6.221%	$127.3696	$127.37	$127.35	$127.40
Purchase #3	$190.26	13.265%	$215.498	$215.50	$215.50	$215.50
Purchase #4	$69.34	10.458%	$76.5916	$76.59	$76.60	$76.60
Purchase #5	$5.47	7.726%	$5.8926	$5.89	$5.90	$5.90
Purchase #6	$248.44	9.858%	$272.9312	$272.93	$272.95	$272.90
Purchase #7	$225.40	12.265%	$253.0453	$253.05	$253.05	$253.00
7 purchase totals =	$971.71		$1,067.8579	$1,067.86	$1,067.90	$1,067.80