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	$189.37	3.547%	$196.087	$196.09	$196.10	$196.10
Purchase #2	$57.56	13.557%	$65.3634	$65.36	$65.35	$65.40
Purchase #3	$249.85	9.475%	$273.5233	$273.52	$273.50	$273.50
Purchase #4	$167.38	9.692%	$183.6025	$183.60	$183.60	$183.60
Purchase #5	$154.94	12.329%	$174.0426	$174.04	$174.05	$174.00
Purchase #6	$76.39	5.492%	$80.5853	$80.59	$80.60	$80.60
Purchase #7	$10.46	10.794%	$11.5891	$11.59	$11.60	$11.60
7 purchase totals =	$905.95		$984.7932	$984.79	$984.80	$984.80