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	$79.64	8.422%	$86.3473	$86.35	$86.35	$86.30
Purchase #2	$6.65	11.846%	$7.4378	$7.44	$7.45	$7.40
Purchase #3	$59.98	13.116%	$67.847	$67.85	$67.85	$67.80
Purchase #4	$79.74	6.734%	$85.1097	$85.11	$85.10	$85.10
Purchase #5	$168.87	3.532%	$174.8345	$174.83	$174.85	$174.80
Purchase #6	$84.32	3.802%	$87.5258	$87.53	$87.55	$87.50
Purchase #7	$121.40	8.395%	$131.5915	$131.59	$131.60	$131.60
7 purchase totals =	$600.60		$640.6936	$640.70	$640.75	$640.50