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	$173.93	4.348%	$181.4925	$181.49	$181.50	$181.50
Purchase #2	$64.76	11.330%	$72.0973	$72.10	$72.10	$72.10
Purchase #3	$139.83	11.690%	$156.1761	$156.18	$156.20	$156.20
Purchase #4	$226.27	13.829%	$257.5609	$257.56	$257.55	$257.60
Purchase #5	$177.45	5.733%	$187.6232	$187.62	$187.60	$187.60
Purchase #6	$50.86	9.786%	$55.8372	$55.84	$55.85	$55.80
Purchase #7	$125.72	9.203%	$137.29	$137.29	$137.30	$137.30
7 purchase totals =	$958.82		$1,048.0772	$1,048.08	$1,048.10	$1,048.10