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	$62.49	12.653%	$70.3969	$70.40	$70.40	$70.40
Purchase #2	$233.46	3.863%	$242.4786	$242.48	$242.50	$242.50
Purchase #3	$65.78	13.857%	$74.8951	$74.90	$74.90	$74.90
Purchase #4	$215.70	13.823%	$245.5162	$245.52	$245.50	$245.50
Purchase #5	$212.52	5.658%	$224.5444	$224.54	$224.55	$224.50
Purchase #6	$71.87	12.556%	$80.894	$80.89	$80.90	$80.90
Purchase #7	$62.81	6.293%	$66.7626	$66.76	$66.75	$66.80
7 purchase totals =	$924.63		$1,005.4878	$1,005.49	$1,005.50	$1,005.50