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	$63.96	13.127%	$72.356	$72.36	$72.35	$72.40
Purchase #2	$132.59	3.729%	$137.5343	$137.53	$137.55	$137.50
Purchase #3	$141.39	13.441%	$160.3942	$160.39	$160.40	$160.40
Purchase #4	$210.83	3.214%	$217.6061	$217.61	$217.60	$217.60
Purchase #5	$231.65	10.795%	$256.6566	$256.66	$256.65	$256.70
Purchase #6	$40.62	9.859%	$44.6247	$44.62	$44.60	$44.60
Purchase #7	$162.41	3.372%	$167.8865	$167.89	$167.90	$167.90
7 purchase totals =	$983.45		$1,057.0584	$1,057.06	$1,057.05	$1,057.10