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	$244.56	6.367%	$260.1311	$260.13	$260.15	$260.10
Purchase #2	$173.45	13.142%	$196.2448	$196.24	$196.25	$196.20
Purchase #3	$30.48	12.487%	$34.286	$34.29	$34.30	$34.30
Purchase #4	$50.59	13.790%	$57.5664	$57.57	$57.55	$57.60
Purchase #5	$88.56	9.722%	$97.1698	$97.17	$97.15	$97.20
Purchase #6	$100.90	5.815%	$106.7673	$106.77	$106.75	$106.80
Purchase #7	$67.58	7.509%	$72.6546	$72.65	$72.65	$72.70
7 purchase totals =	$756.12		$824.8200	$824.82	$824.80	$824.90