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	$78.73	8.456%	$85.3874	$85.39	$85.40	$85.40
Purchase #2	$36.67	8.420%	$39.7576	$39.76	$39.75	$39.80
Purchase #3	$91.37	8.429%	$99.0716	$99.07	$99.05	$99.10
Purchase #4	$18.28	10.110%	$20.1281	$20.13	$20.15	$20.10
Purchase #5	$153.93	10.177%	$169.5955	$169.60	$169.60	$169.60
Purchase #6	$136.87	13.379%	$155.1818	$155.18	$155.20	$155.20
Purchase #7	$231.28	13.443%	$262.371	$262.37	$262.35	$262.40
7 purchase totals =	$747.13		$831.4930	$831.50	$831.50	$831.60