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	$175.50	11.441%	$195.579	$195.58	$195.60	$195.60
Purchase #2	$215.72	4.770%	$226.0098	$226.01	$226.00	$226.00
Purchase #3	$41.90	13.287%	$47.4673	$47.47	$47.45	$47.50
Purchase #4	$189.29	6.461%	$201.52	$201.52	$201.50	$201.50
Purchase #5	$49.43	10.431%	$54.586	$54.59	$54.60	$54.60
Purchase #6	$173.69	9.725%	$190.5814	$190.58	$190.60	$190.60
Purchase #7	$78.99	13.696%	$89.8085	$89.81	$89.80	$89.80
7 purchase totals =	$924.52		$1,005.5520	$1,005.56	$1,005.55	$1,005.60