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	$83.53	7.296%	$89.6243	$89.62	$89.60	$89.60
Purchase #2	$122.32	7.874%	$131.9515	$131.95	$131.95	$132.00
Purchase #3	$69.52	7.440%	$74.6923	$74.69	$74.70	$74.70
Purchase #4	$171.54	5.868%	$181.606	$181.61	$181.60	$181.60
Purchase #5	$7.87	8.105%	$8.5079	$8.51	$8.50	$8.50
Purchase #6	$52.80	13.229%	$59.7849	$59.78	$59.80	$59.80
Purchase #7	$222.30	10.860%	$246.4418	$246.44	$246.45	$246.40
7 purchase totals =	$729.88		$792.6087	$792.60	$792.60	$792.60