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	$184.81	11.637%	$206.3163	$206.32	$206.30	$206.30
Purchase #2	$106.63	9.794%	$117.0733	$117.07	$117.05	$117.10
Purchase #3	$73.73	8.664%	$80.118	$80.12	$80.10	$80.10
Purchase #4	$119.31	10.261%	$131.5524	$131.55	$131.55	$131.60
Purchase #5	$207.88	12.536%	$233.9398	$233.94	$233.95	$233.90
Purchase #6	$97.37	3.184%	$100.4703	$100.47	$100.45	$100.50
Purchase #7	$214.85	8.853%	$233.8707	$233.87	$233.85	$233.90
7 purchase totals =	$1,004.58		$1,103.3408	$1,103.34	$1,103.25	$1,103.40