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	$33.71	5.638%	$35.6106	$35.61	$35.60	$35.60
Purchase #2	$55.72	6.799%	$59.5084	$59.51	$59.50	$59.50
Purchase #3	$248.62	7.158%	$266.4162	$266.42	$266.40	$266.40
Purchase #4	$246.38	4.612%	$257.743	$257.74	$257.75	$257.70
Purchase #5	$131.77	8.851%	$143.433	$143.43	$143.45	$143.40
Purchase #6	$160.33	10.295%	$176.836	$176.84	$176.85	$176.80
Purchase #7	$119.89	3.437%	$124.0106	$124.01	$124.00	$124.00
7 purchase totals =	$996.42		$1,063.5578	$1,063.56	$1,063.55	$1,063.40