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	$43.83	4.696%	$45.8883	$45.89	$45.90	$45.90
Purchase #2	$46.40	6.792%	$49.5515	$49.55	$49.55	$49.60
Purchase #3	$6.67	10.319%	$7.3583	$7.36	$7.35	$7.40
Purchase #4	$94.45	6.432%	$100.525	$100.53	$100.55	$100.50
Purchase #5	$77.52	6.580%	$82.6208	$82.62	$82.60	$82.60
Purchase #6	$13.97	6.820%	$14.9228	$14.92	$14.90	$14.90
Purchase #7	$249.97	5.460%	$263.6184	$263.62	$263.60	$263.60
7 purchase totals =	$532.81		$564.4851	$564.49	$564.45	$564.50