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	$200.44	11.559%	$223.6089	$223.61	$223.60	$223.60
Purchase #2	$111.61	4.724%	$116.8825	$116.88	$116.90	$116.90
Purchase #3	$148.78	6.393%	$158.2915	$158.29	$158.30	$158.30
Purchase #4	$112.25	4.128%	$116.8837	$116.88	$116.90	$116.90
Purchase #5	$151.88	6.107%	$161.1553	$161.16	$161.15	$161.20
Purchase #6	$41.91	6.736%	$44.7331	$44.73	$44.75	$44.70
Purchase #7	$51.33	10.119%	$56.5241	$56.52	$56.50	$56.50
7 purchase totals =	$818.20		$878.0791	$878.07	$878.10	$878.10