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	$158.51	4.148%	$165.085	$165.09	$165.10	$165.10
Purchase #2	$103.39	4.533%	$108.0767	$108.08	$108.10	$108.10
Purchase #3	$125.94	11.151%	$139.9836	$139.98	$140.00	$140.00
Purchase #4	$83.39	13.360%	$94.5309	$94.53	$94.55	$94.50
Purchase #5	$59.95	10.473%	$66.2286	$66.23	$66.25	$66.20
Purchase #6	$67.62	6.569%	$72.062	$72.06	$72.05	$72.10
Purchase #7	$95.65	13.549%	$108.6096	$108.61	$108.60	$108.60
7 purchase totals =	$694.45		$754.5764	$754.58	$754.65	$754.60