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	$141.66	7.756%	$152.6471	$152.65	$152.65	$152.60
Purchase #2	$196.49	13.249%	$222.523	$222.52	$222.50	$222.50
Purchase #3	$13.53	6.852%	$14.4571	$14.46	$14.45	$14.50
Purchase #4	$212.87	13.381%	$241.3541	$241.35	$241.35	$241.40
Purchase #5	$233.93	9.599%	$256.3849	$256.38	$256.40	$256.40
Purchase #6	$175.38	6.390%	$186.5868	$186.59	$186.60	$186.60
Purchase #7	$76.42	6.134%	$81.1076	$81.11	$81.10	$81.10
7 purchase totals =	$1,050.28		$1,155.0606	$1,155.06	$1,155.05	$1,155.10