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	$56.85	6.478%	$60.5327	$60.53	$60.55	$60.50
Purchase #2	$181.80	5.399%	$191.6154	$191.62	$191.60	$191.60
Purchase #3	$153.80	11.359%	$171.2701	$171.27	$171.25	$171.30
Purchase #4	$32.51	10.400%	$35.891	$35.89	$35.90	$35.90
Purchase #5	$126.26	4.868%	$132.4063	$132.41	$132.40	$132.40
Purchase #6	$233.30	9.521%	$255.5125	$255.51	$255.50	$255.50
Purchase #7	$231.85	7.602%	$249.4752	$249.48	$249.50	$249.50
7 purchase totals =	$1,016.37		$1,096.7032	$1,096.71	$1,096.70	$1,096.70