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	$222.25	6.386%	$236.4429	$236.44	$236.45	$236.40
Purchase #2	$98.56	12.863%	$111.2378	$111.24	$111.25	$111.20
Purchase #3	$111.97	7.614%	$120.4954	$120.50	$120.50	$120.50
Purchase #4	$222.72	7.277%	$238.9273	$238.93	$238.95	$238.90
Purchase #5	$72.68	11.215%	$80.8311	$80.83	$80.85	$80.80
Purchase #6	$145.69	5.356%	$153.4932	$153.49	$153.50	$153.50
Purchase #7	$123.89	3.669%	$128.4355	$128.44	$128.45	$128.40
7 purchase totals =	$997.76		$1,069.8632	$1,069.87	$1,069.95	$1,069.70