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	$229.60	12.825%	$259.0462	$259.05	$259.05	$259.00
Purchase #2	$227.66	7.385%	$244.4727	$244.47	$244.45	$244.50
Purchase #3	$240.46	10.789%	$266.4032	$266.40	$266.40	$266.40
Purchase #4	$13.89	9.405%	$15.1964	$15.20	$15.20	$15.20
Purchase #5	$13.56	6.515%	$14.4434	$14.44	$14.45	$14.40
Purchase #6	$162.69	6.264%	$172.8809	$172.88	$172.90	$172.90
Purchase #7	$98.95	13.783%	$112.5883	$112.59	$112.60	$112.60
7 purchase totals =	$986.81		$1,085.0311	$1,085.03	$1,085.05	$1,085.00