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	$81.28	4.657%	$85.0652	$85.07	$85.05	$85.10
Purchase #2	$108.64	5.748%	$114.8846	$114.88	$114.90	$114.90
Purchase #3	$120.59	7.693%	$129.867	$129.87	$129.85	$129.90
Purchase #4	$166.76	13.793%	$189.7612	$189.76	$189.75	$189.80
Purchase #5	$33.65	5.523%	$35.5085	$35.51	$35.50	$35.50
Purchase #6	$160.75	7.238%	$172.3851	$172.39	$172.40	$172.40
Purchase #7	$246.76	13.534%	$280.1565	$280.16	$280.15	$280.20
7 purchase totals =	$918.43		$1,007.6281	$1,007.64	$1,007.60	$1,007.80