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	$236.73	8.442%	$256.7147	$256.71	$256.70	$256.70
Purchase #2	$13.73	12.158%	$15.3993	$15.40	$15.40	$15.40
Purchase #3	$247.60	7.183%	$265.3851	$265.39	$265.40	$265.40
Purchase #4	$150.44	12.861%	$169.7881	$169.79	$169.80	$169.80
Purchase #5	$150.64	8.791%	$163.8828	$163.88	$163.90	$163.90
Purchase #6	$66.82	8.654%	$72.6026	$72.60	$72.60	$72.60
Purchase #7	$50.46	10.264%	$55.6392	$55.64	$55.65	$55.60
7 purchase totals =	$916.42		$999.4118	$999.41	$999.45	$999.40