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	$159.72	12.520%	$179.7169	$179.72	$179.70	$179.70
Purchase #2	$140.71	7.685%	$151.5236	$151.52	$151.50	$151.50
Purchase #3	$128.89	8.482%	$139.8224	$139.82	$139.80	$139.80
Purchase #4	$199.91	10.442%	$220.7846	$220.78	$220.80	$220.80
Purchase #5	$109.88	3.405%	$113.6214	$113.62	$113.60	$113.60
Purchase #6	$60.35	8.210%	$65.3047	$65.30	$65.30	$65.30
Purchase #7	$143.83	8.233%	$155.6715	$155.67	$155.65	$155.70
7 purchase totals =	$943.29		$1,026.4451	$1,026.43	$1,026.35	$1,026.40