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	$101.35	9.607%	$111.0867	$111.09	$111.10	$111.10
Purchase #2	$169.52	4.281%	$176.7772	$176.78	$176.80	$176.80
Purchase #3	$108.77	10.188%	$119.8515	$119.85	$119.85	$119.90
Purchase #4	$237.46	6.794%	$253.593	$253.59	$253.60	$253.60
Purchase #5	$250.88	9.417%	$274.5054	$274.51	$274.50	$274.50
Purchase #6	$45.36	13.752%	$51.5979	$51.60	$51.60	$51.60
Purchase #7	$127.87	8.829%	$139.1596	$139.16	$139.15	$139.20
7 purchase totals =	$1,041.21		$1,126.5713	$1,126.58	$1,126.60	$1,126.70