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	$12.59	6.114%	$13.3598	$13.36	$13.35	$13.40
Purchase #2	$74.77	7.661%	$80.4981	$80.50	$80.50	$80.50
Purchase #3	$128.60	3.614%	$133.2476	$133.25	$133.25	$133.20
Purchase #4	$226.98	12.612%	$255.6067	$255.61	$255.60	$255.60
Purchase #5	$244.27	5.584%	$257.91	$257.91	$257.90	$257.90
Purchase #6	$67.36	5.589%	$71.1248	$71.12	$71.10	$71.10
Purchase #7	$46.90	12.661%	$52.838	$52.84	$52.85	$52.80
7 purchase totals =	$801.47		$864.5850	$864.59	$864.55	$864.50