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	$41.48	4.405%	$43.3072	$43.31	$43.30	$43.30
Purchase #2	$154.58	11.140%	$171.8002	$171.80	$171.80	$171.80
Purchase #3	$198.59	9.564%	$217.5831	$217.58	$217.60	$217.60
Purchase #4	$85.29	4.379%	$89.0248	$89.02	$89.00	$89.00
Purchase #5	$17.44	11.480%	$19.4421	$19.44	$19.45	$19.40
Purchase #6	$206.59	12.828%	$233.0914	$233.09	$233.10	$233.10
Purchase #7	$224.53	6.611%	$239.3737	$239.37	$239.35	$239.40
7 purchase totals =	$928.50		$1,013.6225	$1,013.61	$1,013.60	$1,013.60