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	$107.42	3.504%	$111.184	$111.18	$111.20	$111.20
Purchase #2	$133.37	9.151%	$145.5747	$145.57	$145.55	$145.60
Purchase #3	$127.43	9.440%	$139.4594	$139.46	$139.45	$139.50
Purchase #4	$17.78	10.226%	$19.5982	$19.60	$19.60	$19.60
Purchase #5	$108.63	4.817%	$113.8627	$113.86	$113.85	$113.90
Purchase #6	$174.84	5.236%	$183.9946	$183.99	$184.00	$184.00
Purchase #7	$77.40	6.768%	$82.6384	$82.64	$82.65	$82.60
7 purchase totals =	$746.87		$796.3120	$796.30	$796.30	$796.40