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	$127.86	13.452%	$145.0597	$145.06	$145.05	$145.10
Purchase #2	$142.29	10.138%	$156.7154	$156.72	$156.70	$156.70
Purchase #3	$6.42	13.720%	$7.3008	$7.30	$7.30	$7.30
Purchase #4	$226.51	13.672%	$257.4784	$257.48	$257.50	$257.50
Purchase #5	$213.28	10.536%	$235.7512	$235.75	$235.75	$235.80
Purchase #6	$215.50	8.131%	$233.0223	$233.02	$233.00	$233.00
Purchase #7	$125.52	5.631%	$132.588	$132.59	$132.60	$132.60
7 purchase totals =	$1,057.38		$1,167.9158	$1,167.92	$1,167.90	$1,168.00