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	$23.93	6.484%	$25.4816	$25.48	$25.50	$25.50
Purchase #2	$247.59	3.386%	$255.9734	$255.97	$255.95	$256.00
Purchase #3	$68.47	4.223%	$71.3615	$71.36	$71.35	$71.40
Purchase #4	$104.52	4.537%	$109.2621	$109.26	$109.25	$109.30
Purchase #5	$108.26	13.617%	$123.0018	$123.00	$123.00	$123.00
Purchase #6	$223.52	12.217%	$250.8274	$250.83	$250.85	$250.80
Purchase #7	$148.29	10.389%	$163.6958	$163.70	$163.70	$163.70
7 purchase totals =	$924.58		$999.6036	$999.60	$999.60	$999.70