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	$237.66	8.678%	$258.2841	$258.28	$258.30	$258.30
Purchase #2	$168.95	12.329%	$189.7798	$189.78	$189.80	$189.80
Purchase #3	$143.40	8.138%	$155.0699	$155.07	$155.05	$155.10
Purchase #4	$113.34	3.565%	$117.3806	$117.38	$117.40	$117.40
Purchase #5	$60.70	8.262%	$65.715	$65.72	$65.70	$65.70
Purchase #6	$91.75	12.809%	$103.5023	$103.50	$103.50	$103.50
Purchase #7	$196.67	9.864%	$216.0695	$216.07	$216.05	$216.10
7 purchase totals =	$1,012.47		$1,105.8012	$1,105.80	$1,105.80	$1,105.90