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	$164.62	4.491%	$172.0131	$172.01	$172.00	$172.00
Purchase #2	$225.66	7.123%	$241.7338	$241.73	$241.75	$241.70
Purchase #3	$37.60	10.202%	$41.436	$41.44	$41.45	$41.40
Purchase #4	$92.59	8.431%	$100.3963	$100.40	$100.40	$100.40
Purchase #5	$46.39	3.292%	$47.9172	$47.92	$47.90	$47.90
Purchase #6	$136.85	8.506%	$148.4905	$148.49	$148.50	$148.50
Purchase #7	$176.52	10.731%	$195.4624	$195.46	$195.45	$195.50
7 purchase totals =	$880.23		$947.4493	$947.45	$947.45	$947.40