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	$80.35	6.538%	$85.6033	$85.60	$85.60	$85.60
Purchase #2	$241.42	5.829%	$255.4924	$255.49	$255.50	$255.50
Purchase #3	$212.81	11.623%	$237.5449	$237.54	$237.55	$237.50
Purchase #4	$117.74	8.347%	$127.5678	$127.57	$127.55	$127.60
Purchase #5	$62.91	12.598%	$70.8354	$70.84	$70.85	$70.80
Purchase #6	$139.49	10.688%	$154.3987	$154.40	$154.40	$154.40
Purchase #7	$190.62	4.217%	$198.6584	$198.66	$198.65	$198.70
7 purchase totals =	$1,045.34		$1,130.1009	$1,130.10	$1,130.10	$1,130.10