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	$200.92	8.692%	$218.384	$218.38	$218.40	$218.40
Purchase #2	$228.85	12.176%	$256.7148	$256.71	$256.70	$256.70
Purchase #3	$133.65	5.131%	$140.5076	$140.51	$140.50	$140.50
Purchase #4	$29.27	8.805%	$31.8472	$31.85	$31.85	$31.80
Purchase #5	$139.60	11.303%	$155.379	$155.38	$155.40	$155.40
Purchase #6	$64.39	4.514%	$67.2966	$67.30	$67.30	$67.30
Purchase #7	$206.74	9.439%	$226.2542	$226.25	$226.25	$226.30
7 purchase totals =	$1,003.42		$1,096.3834	$1,096.38	$1,096.40	$1,096.40