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	$20.40	11.382%	$22.7219	$22.72	$22.70	$22.70
Purchase #2	$133.99	5.302%	$141.0941	$141.09	$141.10	$141.10
Purchase #3	$177.41	10.540%	$196.109	$196.11	$196.10	$196.10
Purchase #4	$147.33	6.601%	$157.0553	$157.06	$157.05	$157.10
Purchase #5	$233.92	9.607%	$256.3927	$256.39	$256.40	$256.40
Purchase #6	$183.72	3.646%	$190.4184	$190.42	$190.40	$190.40
Purchase #7	$44.66	3.146%	$46.065	$46.07	$46.05	$46.10
7 purchase totals =	$941.43		$1,009.8564	$1,009.86	$1,009.80	$1,009.90