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	$133.36	8.464%	$144.6476	$144.65	$144.65	$144.60
Purchase #2	$51.74	9.627%	$56.721	$56.72	$56.70	$56.70
Purchase #3	$111.56	6.833%	$119.1829	$119.18	$119.20	$119.20
Purchase #4	$10.59	6.182%	$11.2447	$11.24	$11.25	$11.20
Purchase #5	$50.27	13.178%	$56.8946	$56.89	$56.90	$56.90
Purchase #6	$150.95	3.305%	$155.9389	$155.94	$155.95	$155.90
Purchase #7	$142.46	9.803%	$156.4254	$156.43	$156.45	$156.40
7 purchase totals =	$650.93		$701.0551	$701.05	$701.10	$700.90