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	$32.62	3.405%	$33.7307	$33.73	$33.75	$33.70
Purchase #2	$85.80	5.857%	$90.8253	$90.83	$90.85	$90.80
Purchase #3	$87.91	7.434%	$94.4452	$94.45	$94.45	$94.40
Purchase #4	$236.47	8.833%	$257.3574	$257.36	$257.35	$257.40
Purchase #5	$58.25	6.640%	$62.1178	$62.12	$62.10	$62.10
Purchase #6	$115.62	6.748%	$123.422	$123.42	$123.40	$123.40
Purchase #7	$12.87	4.860%	$13.4955	$13.50	$13.50	$13.50
7 purchase totals =	$629.54		$675.3939	$675.41	$675.40	$675.30