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	$221.33	7.549%	$238.0382	$238.04	$238.05	$238.00
Purchase #2	$129.55	10.243%	$142.8198	$142.82	$142.80	$142.80
Purchase #3	$75.70	12.402%	$85.0883	$85.09	$85.10	$85.10
Purchase #4	$116.75	3.787%	$121.1713	$121.17	$121.15	$121.20
Purchase #5	$136.36	6.210%	$144.828	$144.83	$144.85	$144.80
Purchase #6	$235.98	6.725%	$251.8497	$251.85	$251.85	$251.80
Purchase #7	$82.87	8.706%	$90.0847	$90.08	$90.10	$90.10
7 purchase totals =	$998.54		$1,073.8800	$1,073.88	$1,073.90	$1,073.80