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	$34.38	9.138%	$37.5216	$37.52	$37.50	$37.50
Purchase #2	$62.83	13.765%	$71.4785	$71.48	$71.50	$71.50
Purchase #3	$79.53	6.814%	$84.9492	$84.95	$84.95	$84.90
Purchase #4	$9.90	5.826%	$10.4768	$10.48	$10.50	$10.50
Purchase #5	$206.97	7.471%	$222.4327	$222.43	$222.45	$222.40
Purchase #6	$129.48	7.314%	$138.9502	$138.95	$138.95	$139.00
Purchase #7	$192.79	4.108%	$200.7098	$200.71	$200.70	$200.70
7 purchase totals =	$715.88		$766.5188	$766.52	$766.55	$766.50