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	$152.64	4.545%	$159.5775	$159.58	$159.60	$159.60
Purchase #2	$82.25	10.108%	$90.5638	$90.56	$90.55	$90.60
Purchase #3	$164.38	4.572%	$171.8955	$171.90	$171.90	$171.90
Purchase #4	$46.66	12.418%	$52.4542	$52.45	$52.45	$52.50
Purchase #5	$166.71	10.259%	$183.8128	$183.81	$183.80	$183.80
Purchase #6	$131.84	8.660%	$143.2573	$143.26	$143.25	$143.30
Purchase #7	$66.45	7.673%	$71.5487	$71.55	$71.55	$71.50
7 purchase totals =	$810.93		$873.1098	$873.11	$873.10	$873.20