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	$206.97	4.404%	$216.085	$216.09	$216.10	$216.10
Purchase #2	$54.96	7.533%	$59.1001	$59.10	$59.10	$59.10
Purchase #3	$15.62	13.356%	$17.7062	$17.71	$17.70	$17.70
Purchase #4	$10.34	13.225%	$11.7075	$11.71	$11.70	$11.70
Purchase #5	$7.35	10.242%	$8.1028	$8.10	$8.10	$8.10
Purchase #6	$159.67	6.500%	$170.0486	$170.05	$170.05	$170.00
Purchase #7	$178.93	3.307%	$184.8472	$184.85	$184.85	$184.80
7 purchase totals =	$633.84		$667.5974	$667.61	$667.60	$667.50