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	$117.91	8.491%	$127.9217	$127.92	$127.90	$127.90
Purchase #2	$147.57	4.224%	$153.8034	$153.80	$153.80	$153.80
Purchase #3	$99.80	10.684%	$110.4626	$110.46	$110.45	$110.50
Purchase #4	$27.79	7.240%	$29.802	$29.80	$29.80	$29.80
Purchase #5	$180.82	5.221%	$190.2606	$190.26	$190.25	$190.30
Purchase #6	$51.87	9.736%	$56.9201	$56.92	$56.90	$56.90
Purchase #7	$77.77	6.583%	$82.8896	$82.89	$82.90	$82.90
7 purchase totals =	$703.53		$752.0600	$752.05	$752.00	$752.10