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	$237.59	7.443%	$255.2738	$255.27	$255.25	$255.30
Purchase #2	$60.47	3.718%	$62.7183	$62.72	$62.70	$62.70
Purchase #3	$143.74	11.767%	$160.6539	$160.65	$160.65	$160.70
Purchase #4	$84.81	7.189%	$90.907	$90.91	$90.90	$90.90
Purchase #5	$114.31	7.113%	$122.4409	$122.44	$122.45	$122.40
Purchase #6	$55.83	6.262%	$59.3261	$59.33	$59.35	$59.30
Purchase #7	$185.25	5.725%	$195.8556	$195.86	$195.85	$195.90
7 purchase totals =	$882.00		$947.1756	$947.18	$947.15	$947.20