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	$131.68	3.352%	$136.0939	$136.09	$136.10	$136.10
Purchase #2	$24.57	10.153%	$27.0646	$27.06	$27.05	$27.10
Purchase #3	$240.45	7.617%	$258.7651	$258.77	$258.75	$258.80
Purchase #4	$64.32	4.641%	$67.3051	$67.31	$67.30	$67.30
Purchase #5	$186.89	6.693%	$199.3985	$199.40	$199.40	$199.40
Purchase #6	$227.75	12.314%	$255.7951	$255.80	$255.80	$255.80
Purchase #7	$113.56	5.840%	$120.1919	$120.19	$120.20	$120.20
7 purchase totals =	$989.22		$1,064.6142	$1,064.62	$1,064.60	$1,064.70