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	$103.93	10.127%	$114.455	$114.46	$114.45	$114.50
Purchase #2	$60.42	13.732%	$68.7169	$68.72	$68.70	$68.70
Purchase #3	$54.61	13.448%	$61.954	$61.95	$61.95	$62.00
Purchase #4	$244.51	8.518%	$265.3374	$265.34	$265.35	$265.30
Purchase #5	$56.81	4.759%	$59.5136	$59.51	$59.50	$59.50
Purchase #6	$248.40	6.223%	$263.8579	$263.86	$263.85	$263.90
Purchase #7	$199.57	11.554%	$222.6283	$222.63	$222.65	$222.60
7 purchase totals =	$968.25		$1,056.4631	$1,056.47	$1,056.45	$1,056.50