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	$175.78	7.536%	$189.0268	$189.03	$189.05	$189.00
Purchase #2	$85.47	4.327%	$89.1683	$89.17	$89.15	$89.20
Purchase #3	$91.48	11.111%	$101.6443	$101.64	$101.65	$101.60
Purchase #4	$140.36	9.410%	$153.5679	$153.57	$153.55	$153.60
Purchase #5	$85.92	13.423%	$97.453	$97.45	$97.45	$97.50
Purchase #6	$91.43	3.312%	$94.4582	$94.46	$94.45	$94.50
Purchase #7	$87.59	11.192%	$97.3931	$97.39	$97.40	$97.40
7 purchase totals =	$758.03		$822.7116	$822.71	$822.70	$822.80