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	$231.60	4.843%	$242.8164	$242.82	$242.80	$242.80
Purchase #2	$84.49	3.606%	$87.5367	$87.54	$87.55	$87.50
Purchase #3	$117.34	6.148%	$124.5541	$124.55	$124.55	$124.60
Purchase #4	$142.78	6.792%	$152.4776	$152.48	$152.50	$152.50
Purchase #5	$44.72	9.446%	$48.9443	$48.94	$48.95	$48.90
Purchase #6	$183.88	4.256%	$191.7059	$191.71	$191.70	$191.70
Purchase #7	$222.85	3.425%	$230.4826	$230.48	$230.50	$230.50
7 purchase totals =	$1,027.66		$1,078.5176	$1,078.52	$1,078.55	$1,078.50