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	$64.32	3.286%	$66.4336	$66.43	$66.45	$66.40
Purchase #2	$216.77	11.615%	$241.9478	$241.95	$241.95	$241.90
Purchase #3	$215.81	10.640%	$238.7722	$238.77	$238.75	$238.80
Purchase #4	$114.59	11.368%	$127.6166	$127.62	$127.60	$127.60
Purchase #5	$131.56	13.180%	$148.8996	$148.90	$148.90	$148.90
Purchase #6	$76.31	9.301%	$83.4076	$83.41	$83.40	$83.40
Purchase #7	$185.36	12.184%	$207.9443	$207.94	$207.95	$207.90
7 purchase totals =	$1,004.72		$1,115.0217	$1,115.02	$1,115.00	$1,114.90