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	$136.52	5.295%	$143.7487	$143.75	$143.75	$143.70
Purchase #2	$155.51	6.858%	$166.1749	$166.17	$166.15	$166.20
Purchase #3	$238.30	9.212%	$260.2522	$260.25	$260.25	$260.30
Purchase #4	$185.70	5.785%	$196.4427	$196.44	$196.45	$196.40
Purchase #5	$133.25	13.195%	$150.8323	$150.83	$150.85	$150.80
Purchase #6	$13.78	9.291%	$15.0603	$15.06	$15.05	$15.10
Purchase #7	$112.93	4.510%	$118.0231	$118.02	$118.00	$118.00
7 purchase totals =	$975.99		$1,050.5342	$1,050.52	$1,050.50	$1,050.50