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	$68.26	5.823%	$72.2348	$72.23	$72.25	$72.20
Purchase #2	$18.33	8.836%	$19.9496	$19.95	$19.95	$19.90
Purchase #3	$104.88	7.447%	$112.6904	$112.69	$112.70	$112.70
Purchase #4	$212.76	8.823%	$231.5318	$231.53	$231.55	$231.50
Purchase #5	$75.38	13.845%	$85.8164	$85.82	$85.80	$85.80
Purchase #6	$17.77	11.833%	$19.8727	$19.87	$19.85	$19.90
Purchase #7	$225.87	5.487%	$238.2635	$238.26	$238.25	$238.30
7 purchase totals =	$723.25		$780.3592	$780.35	$780.35	$780.30