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	$69.96	4.126%	$72.8465	$72.85	$72.85	$72.80
Purchase #2	$213.42	10.151%	$235.0843	$235.08	$235.10	$235.10
Purchase #3	$173.90	5.325%	$183.1602	$183.16	$183.15	$183.20
Purchase #4	$46.82	10.581%	$51.774	$51.77	$51.75	$51.80
Purchase #5	$204.47	8.530%	$221.9113	$221.91	$221.90	$221.90
Purchase #6	$42.68	7.379%	$45.8294	$45.83	$45.85	$45.80
Purchase #7	$222.98	3.615%	$231.0407	$231.04	$231.05	$231.00
7 purchase totals =	$974.23		$1,041.6464	$1,041.64	$1,041.65	$1,041.60