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	$118.93	11.375%	$132.4583	$132.46	$132.45	$132.50
Purchase #2	$100.38	4.205%	$104.601	$104.60	$104.60	$104.60
Purchase #3	$100.38	9.434%	$109.8498	$109.85	$109.85	$109.80
Purchase #4	$207.98	5.375%	$219.1589	$219.16	$219.15	$219.20
Purchase #5	$154.59	13.506%	$175.4689	$175.47	$175.45	$175.50
Purchase #6	$100.59	12.107%	$112.7684	$112.77	$112.75	$112.80
Purchase #7	$31.59	8.849%	$34.3854	$34.39	$34.40	$34.40
7 purchase totals =	$814.44		$888.6907	$888.70	$888.65	$888.80