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	$182.93	12.576%	$205.9353	$205.94	$205.95	$205.90
Purchase #2	$49.34	3.846%	$51.2376	$51.24	$51.25	$51.20
Purchase #3	$18.98	7.379%	$20.3805	$20.38	$20.40	$20.40
Purchase #4	$41.88	13.695%	$47.6155	$47.62	$47.60	$47.60
Purchase #5	$226.76	4.210%	$236.3066	$236.31	$236.30	$236.30
Purchase #6	$178.34	11.865%	$199.5	$199.50	$199.50	$199.50
Purchase #7	$231.71	10.712%	$256.5308	$256.53	$256.55	$256.50
7 purchase totals =	$929.94		$1,017.5063	$1,017.52	$1,017.55	$1,017.40