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	$39.65	10.652%	$43.8735	$43.87	$43.85	$43.90
Purchase #2	$155.90	9.272%	$170.355	$170.36	$170.35	$170.40
Purchase #3	$198.49	12.267%	$222.8388	$222.84	$222.85	$222.80
Purchase #4	$226.39	13.428%	$256.7896	$256.79	$256.80	$256.80
Purchase #5	$199.47	12.715%	$224.8326	$224.83	$224.85	$224.80
Purchase #6	$62.34	10.471%	$68.8676	$68.87	$68.85	$68.90
Purchase #7	$114.90	7.788%	$123.8484	$123.85	$123.85	$123.80
7 purchase totals =	$997.14		$1,111.4055	$1,111.41	$1,111.40	$1,111.40