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	$132.78	11.866%	$148.5357	$148.54	$148.55	$148.50
Purchase #2	$50.40	10.628%	$55.7565	$55.76	$55.75	$55.80
Purchase #3	$108.46	9.810%	$119.0999	$119.10	$119.10	$119.10
Purchase #4	$92.66	8.683%	$100.7057	$100.71	$100.70	$100.70
Purchase #5	$54.79	8.405%	$59.3951	$59.40	$59.40	$59.40
Purchase #6	$127.65	3.807%	$132.5096	$132.51	$132.50	$132.50
Purchase #7	$202.92	12.112%	$227.4977	$227.50	$227.50	$227.50
7 purchase totals =	$769.66		$843.5002	$843.52	$843.50	$843.50