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	$103.53	3.184%	$106.8264	$106.83	$106.85	$106.80
Purchase #2	$156.53	10.147%	$172.4131	$172.41	$172.40	$172.40
Purchase #3	$212.27	12.285%	$238.3474	$238.35	$238.35	$238.30
Purchase #4	$134.65	10.167%	$148.3399	$148.34	$148.35	$148.30
Purchase #5	$9.27	3.466%	$9.5913	$9.59	$9.60	$9.60
Purchase #6	$11.42	12.671%	$12.867	$12.87	$12.85	$12.90
Purchase #7	$37.94	11.812%	$42.4215	$42.42	$42.40	$42.40
7 purchase totals =	$665.61		$730.8066	$730.81	$730.80	$730.70