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	$87.71	8.847%	$95.4697	$95.47	$95.45	$95.50
Purchase #2	$28.86	11.870%	$32.2857	$32.29	$32.30	$32.30
Purchase #3	$54.41	12.589%	$61.2597	$61.26	$61.25	$61.30
Purchase #4	$238.59	7.429%	$256.3149	$256.31	$256.30	$256.30
Purchase #5	$123.82	12.472%	$139.2628	$139.26	$139.25	$139.30
Purchase #6	$149.59	9.279%	$163.4705	$163.47	$163.45	$163.50
Purchase #7	$201.59	9.558%	$220.858	$220.86	$220.85	$220.90
7 purchase totals =	$884.57		$968.9213	$968.92	$968.85	$969.10