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	$102.85	8.490%	$111.582	$111.58	$111.60	$111.60
Purchase #2	$158.53	5.614%	$167.4299	$167.43	$167.45	$167.40
Purchase #3	$65.98	10.715%	$73.0498	$73.05	$73.05	$73.00
Purchase #4	$208.57	12.441%	$234.5182	$234.52	$234.50	$234.50
Purchase #5	$11.90	9.518%	$13.0326	$13.03	$13.05	$13.00
Purchase #6	$59.90	11.753%	$66.94	$66.94	$66.95	$66.90
Purchase #7	$95.50	4.291%	$99.5979	$99.60	$99.60	$99.60
7 purchase totals =	$703.23		$766.1504	$766.15	$766.20	$766.00