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	$213.70	8.262%	$231.3559	$231.36	$231.35	$231.40
Purchase #2	$228.66	7.540%	$245.901	$245.90	$245.90	$245.90
Purchase #3	$119.94	13.786%	$136.4749	$136.47	$136.45	$136.50
Purchase #4	$117.80	4.476%	$123.0727	$123.07	$123.05	$123.10
Purchase #5	$174.45	9.546%	$191.103	$191.10	$191.10	$191.10
Purchase #6	$100.32	8.655%	$109.0027	$109.00	$109.00	$109.00
Purchase #7	$108.39	9.320%	$118.4919	$118.49	$118.50	$118.50
7 purchase totals =	$1,063.26		$1,155.4021	$1,155.39	$1,155.35	$1,155.50