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	$41.94	10.434%	$46.316	$46.32	$46.30	$46.30
Purchase #2	$29.74	7.612%	$32.0038	$32.00	$32.00	$32.00
Purchase #3	$31.54	9.222%	$34.4486	$34.45	$34.45	$34.40
Purchase #4	$218.28	4.372%	$227.8232	$227.82	$227.80	$227.80
Purchase #5	$155.30	11.262%	$172.7899	$172.79	$172.80	$172.80
Purchase #6	$179.28	10.585%	$198.2568	$198.26	$198.25	$198.30
Purchase #7	$97.33	12.167%	$109.1721	$109.17	$109.15	$109.20
7 purchase totals =	$753.41		$820.8104	$820.81	$820.75	$820.80