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	$196.79	8.159%	$212.8461	$212.85	$212.85	$212.80
Purchase #2	$31.33	7.202%	$33.5864	$33.59	$33.60	$33.60
Purchase #3	$225.97	10.538%	$249.7827	$249.78	$249.80	$249.80
Purchase #4	$65.99	8.448%	$71.5648	$71.56	$71.55	$71.60
Purchase #5	$6.67	5.591%	$7.0429	$7.04	$7.05	$7.00
Purchase #6	$108.64	3.479%	$112.4196	$112.42	$112.40	$112.40
Purchase #7	$89.53	11.832%	$100.1232	$100.12	$100.10	$100.10
7 purchase totals =	$724.92		$787.3657	$787.36	$787.35	$787.30