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	$168.73	9.102%	$184.0878	$184.09	$184.10	$184.10
Purchase #2	$81.98	4.212%	$85.433	$85.43	$85.45	$85.40
Purchase #3	$100.51	12.859%	$113.4346	$113.43	$113.45	$113.40
Purchase #4	$235.65	9.250%	$257.4476	$257.45	$257.45	$257.40
Purchase #5	$168.98	8.638%	$183.5765	$183.58	$183.60	$183.60
Purchase #6	$194.43	13.859%	$221.3761	$221.38	$221.40	$221.40
Purchase #7	$36.75	11.580%	$41.0057	$41.01	$41.00	$41.00
7 purchase totals =	$987.03		$1,086.3613	$1,086.37	$1,086.45	$1,086.30