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	$213.38	10.106%	$234.9442	$234.94	$234.95	$234.90
Purchase #2	$119.50	3.292%	$123.4339	$123.43	$123.45	$123.40
Purchase #3	$78.71	8.204%	$85.1674	$85.17	$85.15	$85.20
Purchase #4	$16.81	3.344%	$17.3721	$17.37	$17.35	$17.40
Purchase #5	$161.69	10.730%	$179.0393	$179.04	$179.05	$179.00
Purchase #6	$14.78	4.607%	$15.4609	$15.46	$15.45	$15.50
Purchase #7	$83.27	11.523%	$92.8652	$92.87	$92.85	$92.90
7 purchase totals =	$688.14		$748.2830	$748.28	$748.25	$748.30