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	$80.50	7.481%	$86.5222	$86.52	$86.50	$86.50
Purchase #2	$19.62	7.557%	$21.1027	$21.10	$21.10	$21.10
Purchase #3	$177.97	9.225%	$194.3877	$194.39	$194.40	$194.40
Purchase #4	$48.50	8.470%	$52.608	$52.61	$52.60	$52.60
Purchase #5	$247.67	12.803%	$279.3792	$279.38	$279.40	$279.40
Purchase #6	$17.89	8.592%	$19.4271	$19.43	$19.45	$19.40
Purchase #7	$90.73	13.590%	$103.0602	$103.06	$103.05	$103.10
7 purchase totals =	$682.88		$756.4871	$756.49	$756.50	$756.50