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	$59.64	10.116%	$65.6732	$65.67	$65.65	$65.70
Purchase #2	$86.71	4.766%	$90.8426	$90.84	$90.85	$90.80
Purchase #3	$177.42	13.785%	$201.8773	$201.88	$201.90	$201.90
Purchase #4	$87.40	3.250%	$90.2405	$90.24	$90.25	$90.20
Purchase #5	$241.96	5.759%	$255.8945	$255.89	$255.90	$255.90
Purchase #6	$120.66	5.581%	$127.394	$127.39	$127.40	$127.40
Purchase #7	$89.69	8.453%	$97.2715	$97.27	$97.25	$97.30
7 purchase totals =	$863.48		$929.1936	$929.18	$929.20	$929.20