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	$230.63	11.631%	$257.4546	$257.45	$257.45	$257.50
Purchase #2	$236.52	4.214%	$246.487	$246.49	$246.50	$246.50
Purchase #3	$178.65	12.237%	$200.5114	$200.51	$200.50	$200.50
Purchase #4	$210.42	6.140%	$223.3398	$223.34	$223.35	$223.30
Purchase #5	$67.26	6.401%	$71.5653	$71.57	$71.55	$71.60
Purchase #6	$48.57	6.209%	$51.5857	$51.59	$51.60	$51.60
Purchase #7	$102.43	5.329%	$107.8885	$107.89	$107.90	$107.90
7 purchase totals =	$1,074.48		$1,158.8323	$1,158.84	$1,158.85	$1,158.90