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	$12.47	6.517%	$13.2827	$13.28	$13.30	$13.30
Purchase #2	$87.93	7.458%	$94.4878	$94.49	$94.50	$94.50
Purchase #3	$50.40	11.197%	$56.0433	$56.04	$56.05	$56.00
Purchase #4	$78.30	3.235%	$80.833	$80.83	$80.85	$80.80
Purchase #5	$71.52	8.228%	$77.4047	$77.40	$77.40	$77.40
Purchase #6	$163.54	13.406%	$185.4642	$185.46	$185.45	$185.50
Purchase #7	$211.89	9.301%	$231.5979	$231.60	$231.60	$231.60
7 purchase totals =	$676.05		$739.1136	$739.10	$739.15	$739.10