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	$207.83	9.446%	$227.4616	$227.46	$227.45	$227.50
Purchase #2	$25.52	13.467%	$28.9568	$28.96	$28.95	$29.00
Purchase #3	$54.48	9.247%	$59.5178	$59.52	$59.50	$59.50
Purchase #4	$28.74	10.874%	$31.8652	$31.87	$31.85	$31.90
Purchase #5	$162.60	5.827%	$172.0747	$172.07	$172.05	$172.10
Purchase #6	$176.43	4.299%	$184.0147	$184.01	$184.00	$184.00
Purchase #7	$43.33	12.680%	$48.8242	$48.82	$48.80	$48.80
7 purchase totals =	$698.93		$752.7150	$752.71	$752.60	$752.80