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	$181.42	13.540%	$205.9843	$205.98	$206.00	$206.00
Purchase #2	$29.65	8.230%	$32.0902	$32.09	$32.10	$32.10
Purchase #3	$104.27	12.244%	$117.0368	$117.04	$117.05	$117.00
Purchase #4	$124.58	10.684%	$137.8901	$137.89	$137.90	$137.90
Purchase #5	$38.68	11.836%	$43.2582	$43.26	$43.25	$43.30
Purchase #6	$65.90	9.604%	$72.229	$72.23	$72.25	$72.20
Purchase #7	$94.46	13.731%	$107.4303	$107.43	$107.45	$107.40
7 purchase totals =	$638.96		$715.9189	$715.92	$716.00	$715.90