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	$47.80	8.187%	$51.7134	$51.71	$51.70	$51.70
Purchase #2	$74.27	3.628%	$76.9645	$76.96	$76.95	$77.00
Purchase #3	$106.41	5.789%	$112.5701	$112.57	$112.55	$112.60
Purchase #4	$205.89	9.572%	$225.5978	$225.60	$225.60	$225.60
Purchase #5	$140.90	6.576%	$150.1656	$150.17	$150.15	$150.20
Purchase #6	$112.49	9.546%	$123.2283	$123.23	$123.25	$123.20
Purchase #7	$244.57	12.373%	$274.8306	$274.83	$274.85	$274.80
7 purchase totals =	$932.33		$1,015.0703	$1,015.07	$1,015.05	$1,015.10