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	$197.91	13.475%	$224.5784	$224.58	$224.60	$224.60
Purchase #2	$18.62	10.173%	$20.5142	$20.51	$20.50	$20.50
Purchase #3	$155.99	4.394%	$162.8442	$162.84	$162.85	$162.80
Purchase #4	$177.67	7.527%	$191.0432	$191.04	$191.05	$191.00
Purchase #5	$112.85	5.538%	$119.0996	$119.10	$119.10	$119.10
Purchase #6	$96.66	13.291%	$109.5071	$109.51	$109.50	$109.50
Purchase #7	$142.25	7.191%	$152.4792	$152.48	$152.50	$152.50
7 purchase totals =	$901.95		$980.0659	$980.06	$980.10	$980.00