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	$141.85	9.572%	$155.4279	$155.43	$155.45	$155.40
Purchase #2	$166.77	9.732%	$183.0001	$183.00	$183.00	$183.00
Purchase #3	$62.60	3.198%	$64.6019	$64.60	$64.60	$64.60
Purchase #4	$155.30	6.233%	$164.9798	$164.98	$165.00	$165.00
Purchase #5	$87.36	13.862%	$99.4698	$99.47	$99.45	$99.50
Purchase #6	$154.68	6.792%	$165.1859	$165.19	$165.20	$165.20
Purchase #7	$92.88	13.446%	$105.3686	$105.37	$105.35	$105.40
7 purchase totals =	$861.44		$938.0340	$938.04	$938.05	$938.10