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	$102.48	9.147%	$111.8538	$111.85	$111.85	$111.90
Purchase #2	$215.85	4.457%	$225.4704	$225.47	$225.45	$225.50
Purchase #3	$52.39	12.624%	$59.0037	$59.00	$59.00	$59.00
Purchase #4	$46.37	6.369%	$49.3233	$49.32	$49.30	$49.30
Purchase #5	$175.49	5.411%	$184.9858	$184.99	$185.00	$185.00
Purchase #6	$92.58	8.736%	$100.6678	$100.67	$100.65	$100.70
Purchase #7	$134.28	7.410%	$144.2301	$144.23	$144.25	$144.20
7 purchase totals =	$819.44		$875.5349	$875.53	$875.50	$875.60