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	$56.48	5.289%	$59.4672	$59.47	$59.45	$59.50
Purchase #2	$189.50	8.494%	$205.5961	$205.60	$205.60	$205.60
Purchase #3	$145.80	10.385%	$160.9413	$160.94	$160.95	$160.90
Purchase #4	$7.70	7.335%	$8.2648	$8.26	$8.25	$8.30
Purchase #5	$41.58	11.847%	$46.506	$46.51	$46.50	$46.50
Purchase #6	$19.97	7.642%	$21.4961	$21.50	$21.50	$21.50
Purchase #7	$183.51	9.316%	$200.6058	$200.61	$200.60	$200.60
7 purchase totals =	$644.54		$702.8773	$702.89	$702.85	$702.90