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	$111.82	4.640%	$117.0084	$117.01	$117.00	$117.00
Purchase #2	$48.90	5.295%	$51.4893	$51.49	$51.50	$51.50
Purchase #3	$172.38	5.375%	$181.6454	$181.65	$181.65	$181.60
Purchase #4	$126.62	8.618%	$137.5321	$137.53	$137.55	$137.50
Purchase #5	$75.72	9.108%	$82.6166	$82.62	$82.60	$82.60
Purchase #6	$108.87	10.480%	$120.2796	$120.28	$120.30	$120.30
Purchase #7	$134.43	7.527%	$144.5485	$144.55	$144.55	$144.50
7 purchase totals =	$778.74		$835.1199	$835.13	$835.15	$835.00