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	$59.98	6.485%	$63.8697	$63.87	$63.85	$63.90
Purchase #2	$43.90	4.755%	$45.9874	$45.99	$46.00	$46.00
Purchase #3	$87.65	7.411%	$94.1457	$94.15	$94.15	$94.10
Purchase #4	$95.36	11.535%	$106.3598	$106.36	$106.35	$106.40
Purchase #5	$140.63	8.103%	$152.0252	$152.03	$152.05	$152.00
Purchase #6	$190.64	3.257%	$196.8491	$196.85	$196.85	$196.80
Purchase #7	$6.80	8.627%	$7.3866	$7.39	$7.40	$7.40
7 purchase totals =	$624.96		$666.6235	$666.64	$666.65	$666.60