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	$217.67	9.345%	$238.0113	$238.01	$238.00	$238.00
Purchase #2	$88.57	13.607%	$100.6217	$100.62	$100.60	$100.60
Purchase #3	$44.73	7.193%	$47.9474	$47.95	$47.95	$47.90
Purchase #4	$57.28	3.865%	$59.4939	$59.49	$59.50	$59.50
Purchase #5	$71.85	4.692%	$75.2212	$75.22	$75.20	$75.20
Purchase #6	$18.45	8.795%	$20.0727	$20.07	$20.05	$20.10
Purchase #7	$17.86	9.179%	$19.4994	$19.50	$19.50	$19.50
7 purchase totals =	$516.41		$560.8676	$560.86	$560.80	$560.80