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	$95.73	5.349%	$100.8506	$100.85	$100.85	$100.90
Purchase #2	$164.61	7.426%	$176.8339	$176.83	$176.85	$176.80
Purchase #3	$109.70	7.384%	$117.8002	$117.80	$117.80	$117.80
Purchase #4	$167.56	6.343%	$178.1883	$178.19	$178.20	$178.20
Purchase #5	$143.69	7.610%	$154.6248	$154.62	$154.60	$154.60
Purchase #6	$124.46	10.745%	$137.8332	$137.83	$137.85	$137.80
Purchase #7	$52.47	5.775%	$55.5001	$55.50	$55.50	$55.50
7 purchase totals =	$858.22		$921.6311	$921.62	$921.65	$921.60