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	$241.25	7.548%	$259.4596	$259.46	$259.45	$259.50
Purchase #2	$81.92	10.614%	$90.615	$90.62	$90.60	$90.60
Purchase #3	$56.36	10.163%	$62.0879	$62.09	$62.10	$62.10
Purchase #4	$83.32	10.295%	$91.8978	$91.90	$91.90	$91.90
Purchase #5	$69.70	3.420%	$72.0837	$72.08	$72.10	$72.10
Purchase #6	$18.58	4.763%	$19.465	$19.47	$19.45	$19.50
Purchase #7	$193.58	12.379%	$217.5433	$217.54	$217.55	$217.50
7 purchase totals =	$744.71		$813.1523	$813.16	$813.15	$813.20