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	$78.66	4.776%	$82.4168	$82.42	$82.40	$82.40
Purchase #2	$104.29	6.770%	$111.3504	$111.35	$111.35	$111.40
Purchase #3	$163.41	6.834%	$174.5774	$174.58	$174.60	$174.60
Purchase #4	$16.53	13.296%	$18.7278	$18.73	$18.75	$18.70
Purchase #5	$20.40	13.548%	$23.1638	$23.16	$23.15	$23.20
Purchase #6	$225.46	12.681%	$254.0506	$254.05	$254.05	$254.10
Purchase #7	$132.66	5.429%	$139.8621	$139.86	$139.85	$139.90
7 purchase totals =	$741.41		$804.1489	$804.15	$804.15	$804.30