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	$135.72	6.602%	$144.6802	$144.68	$144.70	$144.70
Purchase #2	$97.89	12.167%	$109.8003	$109.80	$109.80	$109.80
Purchase #3	$106.33	9.758%	$116.7057	$116.71	$116.70	$116.70
Purchase #4	$111.56	4.337%	$116.3984	$116.40	$116.40	$116.40
Purchase #5	$138.36	3.314%	$142.9453	$142.95	$142.95	$142.90
Purchase #6	$137.80	7.728%	$148.4492	$148.45	$148.45	$148.40
Purchase #7	$201.72	8.871%	$219.6146	$219.61	$219.60	$219.60
7 purchase totals =	$929.38		$998.5937	$998.60	$998.60	$998.50