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	$141.50	13.841%	$161.085	$161.09	$161.10	$161.10
Purchase #2	$59.31	12.598%	$66.7819	$66.78	$66.80	$66.80
Purchase #3	$98.67	13.372%	$111.8642	$111.86	$111.85	$111.90
Purchase #4	$85.49	13.336%	$96.8909	$96.89	$96.90	$96.90
Purchase #5	$29.80	10.424%	$32.9064	$32.91	$32.90	$32.90
Purchase #6	$95.73	8.817%	$104.1705	$104.17	$104.15	$104.20
Purchase #7	$96.48	12.792%	$108.8217	$108.82	$108.80	$108.80
7 purchase totals =	$606.98		$682.5206	$682.52	$682.50	$682.60