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	$174.93	8.623%	$190.0142	$190.01	$190.00	$190.00
Purchase #2	$110.43	6.574%	$117.6897	$117.69	$117.70	$117.70
Purchase #3	$54.82	3.122%	$56.5315	$56.53	$56.55	$56.50
Purchase #4	$97.96	13.414%	$111.1004	$111.10	$111.10	$111.10
Purchase #5	$164.41	11.524%	$183.3566	$183.36	$183.35	$183.40
Purchase #6	$40.60	7.841%	$43.7834	$43.78	$43.80	$43.80
Purchase #7	$153.30	3.227%	$158.247	$158.25	$158.25	$158.20
7 purchase totals =	$796.45		$860.7228	$860.72	$860.75	$860.70