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	$162.64	5.765%	$172.0162	$172.02	$172.00	$172.00
Purchase #2	$104.26	11.828%	$116.5919	$116.59	$116.60	$116.60
Purchase #3	$244.90	8.783%	$266.4096	$266.41	$266.40	$266.40
Purchase #4	$168.62	4.457%	$176.1354	$176.14	$176.15	$176.10
Purchase #5	$57.50	7.839%	$62.0074	$62.01	$62.00	$62.00
Purchase #6	$97.41	7.639%	$104.8511	$104.85	$104.85	$104.90
Purchase #7	$135.89	9.561%	$148.8824	$148.88	$148.90	$148.90
7 purchase totals =	$971.22		$1,046.8940	$1,046.90	$1,046.90	$1,046.90