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	$22.60	5.626%	$23.8715	$23.87	$23.85	$23.90
Purchase #2	$153.76	7.702%	$165.6026	$165.60	$165.60	$165.60
Purchase #3	$100.54	10.245%	$110.8403	$110.84	$110.85	$110.80
Purchase #4	$211.91	9.399%	$231.8274	$231.83	$231.85	$231.80
Purchase #5	$109.92	12.129%	$123.2522	$123.25	$123.25	$123.30
Purchase #6	$107.83	7.661%	$116.0909	$116.09	$116.10	$116.10
Purchase #7	$201.61	13.336%	$228.4967	$228.50	$228.50	$228.50
7 purchase totals =	$908.17		$999.9816	$999.98	$1,000.00	$1,000.00