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	$130.78	12.413%	$147.0137	$147.01	$147.00	$147.00
Purchase #2	$32.42	8.406%	$35.1452	$35.15	$35.15	$35.10
Purchase #3	$234.45	10.293%	$258.5819	$258.58	$258.60	$258.60
Purchase #4	$156.74	7.559%	$168.588	$168.59	$168.60	$168.60
Purchase #5	$60.91	7.162%	$65.2724	$65.27	$65.25	$65.30
Purchase #6	$170.59	11.286%	$189.8428	$189.84	$189.85	$189.80
Purchase #7	$211.28	10.564%	$233.5996	$233.60	$233.60	$233.60
7 purchase totals =	$997.17		$1,098.0436	$1,098.04	$1,098.05	$1,098.00