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	$225.72	3.467%	$233.5457	$233.55	$233.55	$233.50
Purchase #2	$247.63	7.236%	$265.5485	$265.55	$265.55	$265.50
Purchase #3	$25.89	10.430%	$28.5903	$28.59	$28.60	$28.60
Purchase #4	$18.26	5.550%	$19.2734	$19.27	$19.25	$19.30
Purchase #5	$183.86	8.874%	$200.1757	$200.18	$200.20	$200.20
Purchase #6	$122.93	7.275%	$131.8732	$131.87	$131.85	$131.90
Purchase #7	$48.51	11.494%	$54.0857	$54.09	$54.10	$54.10
7 purchase totals =	$872.80		$933.0925	$933.10	$933.10	$933.10