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	$52.72	7.378%	$56.6097	$56.61	$56.60	$56.60
Purchase #2	$68.47	6.583%	$72.9774	$72.98	$73.00	$73.00
Purchase #3	$247.38	7.206%	$265.2062	$265.21	$265.20	$265.20
Purchase #4	$151.98	8.216%	$164.4667	$164.47	$164.45	$164.50
Purchase #5	$215.62	3.542%	$223.2573	$223.26	$223.25	$223.30
Purchase #6	$239.35	11.153%	$266.0447	$266.04	$266.05	$266.00
Purchase #7	$12.36	6.549%	$13.1695	$13.17	$13.15	$13.20
7 purchase totals =	$987.88		$1,061.7315	$1,061.74	$1,061.70	$1,061.80