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	$132.67	7.108%	$142.1002	$142.10	$142.10	$142.10
Purchase #2	$31.34	4.105%	$32.6265	$32.63	$32.65	$32.60
Purchase #3	$167.50	6.271%	$178.0039	$178.00	$178.00	$178.00
Purchase #4	$164.25	9.508%	$179.8669	$179.87	$179.85	$179.90
Purchase #5	$222.88	11.564%	$248.6538	$248.65	$248.65	$248.70
Purchase #6	$210.89	6.618%	$224.8467	$224.85	$224.85	$224.80
Purchase #7	$38.85	4.625%	$40.6468	$40.65	$40.65	$40.60
7 purchase totals =	$968.38		$1,046.7448	$1,046.75	$1,046.75	$1,046.70