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	$207.56	8.368%	$224.9286	$224.93	$224.95	$224.90
Purchase #2	$136.34	11.654%	$152.2291	$152.23	$152.25	$152.20
Purchase #3	$171.77	4.571%	$179.6216	$179.62	$179.60	$179.60
Purchase #4	$6.32	5.256%	$6.6522	$6.65	$6.65	$6.70
Purchase #5	$226.43	13.262%	$256.4591	$256.46	$256.45	$256.50
Purchase #6	$48.55	11.845%	$54.3007	$54.30	$54.30	$54.30
Purchase #7	$109.83	3.294%	$113.4478	$113.45	$113.45	$113.40
7 purchase totals =	$906.80		$987.6391	$987.64	$987.65	$987.60