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	$42.40	11.779%	$47.3943	$47.39	$47.40	$47.40
Purchase #2	$73.30	4.246%	$76.4123	$76.41	$76.40	$76.40
Purchase #3	$52.66	3.812%	$54.6674	$54.67	$54.65	$54.70
Purchase #4	$107.45	10.568%	$118.8053	$118.81	$118.80	$118.80
Purchase #5	$223.32	7.790%	$240.7166	$240.72	$240.70	$240.70
Purchase #6	$97.33	3.278%	$100.5205	$100.52	$100.50	$100.50
Purchase #7	$214.30	6.798%	$228.8681	$228.87	$228.85	$228.90
7 purchase totals =	$810.76		$867.3845	$867.39	$867.30	$867.40