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	$63.35	3.574%	$65.6141	$65.61	$65.60	$65.60
Purchase #2	$246.35	5.638%	$260.2392	$260.24	$260.25	$260.20
Purchase #3	$141.47	7.452%	$152.0123	$152.01	$152.00	$152.00
Purchase #4	$177.71	7.612%	$191.2373	$191.24	$191.25	$191.20
Purchase #5	$10.44	11.307%	$11.6205	$11.62	$11.60	$11.60
Purchase #6	$61.89	13.318%	$70.1325	$70.13	$70.15	$70.10
Purchase #7	$246.59	7.559%	$265.2297	$265.23	$265.25	$265.20
7 purchase totals =	$947.80		$1,016.0856	$1,016.08	$1,016.10	$1,015.90