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	$220.79	4.636%	$231.0258	$231.03	$231.05	$231.00
Purchase #2	$185.35	6.188%	$196.8195	$196.82	$196.80	$196.80
Purchase #3	$84.97	8.285%	$92.0098	$92.01	$92.00	$92.00
Purchase #4	$168.76	10.124%	$185.8453	$185.85	$185.85	$185.80
Purchase #5	$114.37	10.358%	$126.2164	$126.22	$126.20	$126.20
Purchase #6	$116.66	5.789%	$123.4134	$123.41	$123.40	$123.40
Purchase #7	$151.47	4.536%	$158.3407	$158.34	$158.35	$158.30
7 purchase totals =	$1,042.37		$1,113.6709	$1,113.68	$1,113.65	$1,113.50