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	$32.38	8.510%	$35.1355	$35.14	$35.15	$35.10
Purchase #2	$90.35	11.213%	$100.4809	$100.48	$100.50	$100.50
Purchase #3	$94.72	5.635%	$100.0575	$100.06	$100.05	$100.10
Purchase #4	$95.65	11.154%	$106.3188	$106.32	$106.30	$106.30
Purchase #5	$29.26	9.459%	$32.0277	$32.03	$32.05	$32.00
Purchase #6	$51.48	10.188%	$56.7248	$56.72	$56.70	$56.70
Purchase #7	$44.52	13.318%	$50.4492	$50.45	$50.45	$50.40
7 purchase totals =	$438.36		$481.1944	$481.20	$481.20	$481.10