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	$207.56	7.616%	$223.3678	$223.37	$223.35	$223.40
Purchase #2	$83.52	8.200%	$90.3686	$90.37	$90.35	$90.40
Purchase #3	$82.53	5.836%	$87.3465	$87.35	$87.35	$87.30
Purchase #4	$127.28	13.753%	$144.7848	$144.78	$144.80	$144.80
Purchase #5	$18.25	5.265%	$19.2109	$19.21	$19.20	$19.20
Purchase #6	$169.81	13.320%	$192.4287	$192.43	$192.45	$192.40
Purchase #7	$11.54	8.624%	$12.5352	$12.54	$12.55	$12.50
7 purchase totals =	$700.49		$770.0425	$770.05	$770.05	$770.00