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	$56.83	10.656%	$62.8858	$62.89	$62.90	$62.90
Purchase #2	$122.42	7.135%	$131.1547	$131.15	$131.15	$131.20
Purchase #3	$249.48	4.685%	$261.1681	$261.17	$261.15	$261.20
Purchase #4	$50.27	5.764%	$53.1676	$53.17	$53.15	$53.20
Purchase #5	$171.45	3.736%	$177.8554	$177.86	$177.85	$177.90
Purchase #6	$66.42	7.559%	$71.4407	$71.44	$71.45	$71.40
Purchase #7	$111.81	11.598%	$124.7777	$124.78	$124.80	$124.80
7 purchase totals =	$828.68		$882.4500	$882.46	$882.45	$882.60