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	$238.81	8.756%	$259.7202	$259.72	$259.70	$259.70
Purchase #2	$50.56	3.486%	$52.3225	$52.32	$52.30	$52.30
Purchase #3	$109.80	12.820%	$123.8764	$123.88	$123.90	$123.90
Purchase #4	$81.43	13.682%	$92.5713	$92.57	$92.55	$92.60
Purchase #5	$165.27	11.849%	$184.8528	$184.85	$184.85	$184.90
Purchase #6	$167.81	5.339%	$176.7694	$176.77	$176.75	$176.80
Purchase #7	$128.44	7.874%	$138.5534	$138.55	$138.55	$138.60
7 purchase totals =	$942.12		$1,028.6660	$1,028.66	$1,028.60	$1,028.80