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	$85.70	7.839%	$92.418	$92.42	$92.40	$92.40
Purchase #2	$94.39	11.833%	$105.5592	$105.56	$105.55	$105.60
Purchase #3	$69.68	3.849%	$72.362	$72.36	$72.35	$72.40
Purchase #4	$108.41	10.690%	$119.999	$120.00	$120.00	$120.00
Purchase #5	$149.99	5.817%	$158.7149	$158.71	$158.70	$158.70
Purchase #6	$77.77	4.820%	$81.5185	$81.52	$81.50	$81.50
Purchase #7	$127.35	13.755%	$144.867	$144.87	$144.85	$144.90
7 purchase totals =	$713.29		$775.4386	$775.44	$775.35	$775.50