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	$61.27	4.207%	$63.8476	$63.85	$63.85	$63.80
Purchase #2	$85.90	5.780%	$90.865	$90.87	$90.85	$90.90
Purchase #3	$222.61	4.866%	$233.4422	$233.44	$233.45	$233.40
Purchase #4	$131.76	4.501%	$137.6905	$137.69	$137.70	$137.70
Purchase #5	$132.83	9.359%	$145.2616	$145.26	$145.25	$145.30
Purchase #6	$29.70	9.424%	$32.4989	$32.50	$32.50	$32.50
Purchase #7	$233.62	9.282%	$255.3046	$255.30	$255.30	$255.30
7 purchase totals =	$897.69		$958.9104	$958.91	$958.90	$958.90