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	$200.69	7.277%	$215.2942	$215.29	$215.30	$215.30
Purchase #2	$67.35	13.650%	$76.5433	$76.54	$76.55	$76.50
Purchase #3	$137.53	5.730%	$145.4105	$145.41	$145.40	$145.40
Purchase #4	$83.29	7.284%	$89.3568	$89.36	$89.35	$89.40
Purchase #5	$96.36	7.105%	$103.2064	$103.21	$103.20	$103.20
Purchase #6	$132.69	3.136%	$136.8512	$136.85	$136.85	$136.90
Purchase #7	$14.67	6.235%	$15.5847	$15.58	$15.60	$15.60
7 purchase totals =	$732.58		$782.2471	$782.24	$782.25	$782.30