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	$40.38	5.528%	$42.6122	$42.61	$42.60	$42.60
Purchase #2	$10.25	8.258%	$11.0964	$11.10	$11.10	$11.10
Purchase #3	$99.70	6.506%	$106.1865	$106.19	$106.20	$106.20
Purchase #4	$79.93	10.231%	$88.1076	$88.11	$88.10	$88.10
Purchase #5	$107.52	10.757%	$119.0859	$119.09	$119.10	$119.10
Purchase #6	$100.48	8.605%	$109.1263	$109.13	$109.15	$109.10
Purchase #7	$81.41	11.589%	$90.8446	$90.84	$90.85	$90.80
7 purchase totals =	$519.67		$567.0595	$567.07	$567.10	$567.00