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	$183.77	12.488%	$206.7192	$206.72	$206.70	$206.70
Purchase #2	$148.57	4.803%	$155.7058	$155.71	$155.70	$155.70
Purchase #3	$27.64	4.539%	$28.8946	$28.89	$28.90	$28.90
Purchase #4	$48.33	13.606%	$54.9058	$54.91	$54.90	$54.90
Purchase #5	$18.37	13.632%	$20.8742	$20.87	$20.85	$20.90
Purchase #6	$143.97	7.487%	$154.749	$154.75	$154.75	$154.70
Purchase #7	$28.68	9.580%	$31.4275	$31.43	$31.45	$31.40
7 purchase totals =	$599.33		$653.2761	$653.28	$653.25	$653.20