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	$192.38	13.666%	$218.6707	$218.67	$218.65	$218.70
Purchase #2	$86.32	13.604%	$98.063	$98.06	$98.05	$98.10
Purchase #3	$183.87	3.604%	$190.4967	$190.50	$190.50	$190.50
Purchase #4	$120.31	11.159%	$133.7354	$133.74	$133.75	$133.70
Purchase #5	$126.91	8.228%	$137.3522	$137.35	$137.35	$137.40
Purchase #6	$38.31	11.277%	$42.6302	$42.63	$42.65	$42.60
Purchase #7	$106.74	4.594%	$111.6436	$111.64	$111.65	$111.60
7 purchase totals =	$854.84		$932.5918	$932.59	$932.60	$932.60