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	$97.96	13.691%	$111.3717	$111.37	$111.35	$111.40
Purchase #2	$187.96	4.292%	$196.0272	$196.03	$196.05	$196.00
Purchase #3	$15.83	10.690%	$17.5222	$17.52	$17.50	$17.50
Purchase #4	$115.52	9.169%	$126.112	$126.11	$126.10	$126.10
Purchase #5	$110.50	13.519%	$125.4385	$125.44	$125.45	$125.40
Purchase #6	$131.85	5.111%	$138.5889	$138.59	$138.60	$138.60
Purchase #7	$117.40	13.736%	$133.5261	$133.53	$133.55	$133.50
7 purchase totals =	$777.02		$848.5866	$848.59	$848.60	$848.50