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	$79.26	4.197%	$82.5865	$82.59	$82.60	$82.60
Purchase #2	$178.41	7.452%	$191.7051	$191.71	$191.70	$191.70
Purchase #3	$83.98	13.741%	$95.5197	$95.52	$95.50	$95.50
Purchase #4	$220.33	8.556%	$239.1814	$239.18	$239.20	$239.20
Purchase #5	$123.85	3.209%	$127.8243	$127.82	$127.80	$127.80
Purchase #6	$32.67	7.325%	$35.0631	$35.06	$35.05	$35.10
Purchase #7	$178.37	6.612%	$190.1638	$190.16	$190.15	$190.20
7 purchase totals =	$896.87		$962.0439	$962.04	$962.00	$962.10