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	$28.77	11.475%	$32.0714	$32.07	$32.05	$32.10
Purchase #2	$235.89	8.367%	$255.6269	$255.63	$255.65	$255.60
Purchase #3	$155.32	6.528%	$165.4593	$165.46	$165.45	$165.50
Purchase #4	$87.56	8.368%	$94.887	$94.89	$94.90	$94.90
Purchase #5	$32.27	10.730%	$35.7326	$35.73	$35.75	$35.70
Purchase #6	$50.72	6.454%	$53.9935	$53.99	$54.00	$54.00
Purchase #7	$123.98	7.135%	$132.826	$132.83	$132.85	$132.80
7 purchase totals =	$714.51		$770.5967	$770.60	$770.65	$770.60