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	$57.30	9.463%	$62.7223	$62.72	$62.70	$62.70
Purchase #2	$194.86	8.256%	$210.9476	$210.95	$210.95	$210.90
Purchase #3	$160.83	12.458%	$180.8662	$180.87	$180.85	$180.90
Purchase #4	$139.63	10.680%	$154.5425	$154.54	$154.55	$154.50
Purchase #5	$244.78	6.416%	$260.4851	$260.49	$260.50	$260.50
Purchase #6	$138.89	13.348%	$157.429	$157.43	$157.45	$157.40
Purchase #7	$135.27	7.566%	$145.5045	$145.50	$145.50	$145.50
7 purchase totals =	$1,071.56		$1,172.4972	$1,172.50	$1,172.50	$1,172.40