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	$172.82	5.664%	$182.6085	$182.61	$182.60	$182.60
Purchase #2	$24.42	11.240%	$27.1648	$27.16	$27.15	$27.20
Purchase #3	$208.98	11.724%	$233.4808	$233.48	$233.50	$233.50
Purchase #4	$28.26	11.466%	$31.5003	$31.50	$31.50	$31.50
Purchase #5	$183.90	13.329%	$208.412	$208.41	$208.40	$208.40
Purchase #6	$6.39	4.393%	$6.6707	$6.67	$6.65	$6.70
Purchase #7	$197.58	13.809%	$224.8638	$224.86	$224.85	$224.90
7 purchase totals =	$822.35		$914.7009	$914.69	$914.65	$914.80