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	$162.27	6.519%	$172.8484	$172.85	$172.85	$172.80
Purchase #2	$7.68	12.377%	$8.6306	$8.63	$8.65	$8.60
Purchase #3	$101.88	6.476%	$108.4777	$108.48	$108.50	$108.50
Purchase #4	$223.35	6.817%	$238.5758	$238.58	$238.60	$238.60
Purchase #5	$47.35	9.300%	$51.7536	$51.75	$51.75	$51.80
Purchase #6	$146.75	12.246%	$164.721	$164.72	$164.70	$164.70
Purchase #7	$36.98	12.145%	$41.4712	$41.47	$41.45	$41.50
7 purchase totals =	$726.26		$786.4783	$786.48	$786.50	$786.50