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	$95.26	3.630%	$98.7179	$98.72	$98.70	$98.70
Purchase #2	$105.53	5.599%	$111.4386	$111.44	$111.45	$111.40
Purchase #3	$90.91	10.862%	$100.7846	$100.78	$100.80	$100.80
Purchase #4	$169.62	4.260%	$176.8458	$176.85	$176.85	$176.80
Purchase #5	$15.72	10.495%	$17.3698	$17.37	$17.35	$17.40
Purchase #6	$247.83	7.548%	$266.5362	$266.54	$266.55	$266.50
Purchase #7	$137.87	10.446%	$152.2719	$152.27	$152.25	$152.30
7 purchase totals =	$862.74		$923.9648	$923.97	$923.95	$923.90