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	$128.46	9.189%	$140.2642	$140.26	$140.25	$140.30
Purchase #2	$212.38	12.462%	$238.8468	$238.85	$238.85	$238.80
Purchase #3	$107.39	8.704%	$116.7372	$116.74	$116.75	$116.70
Purchase #4	$188.34	13.167%	$213.1387	$213.14	$213.15	$213.10
Purchase #5	$34.75	3.405%	$35.9332	$35.93	$35.95	$35.90
Purchase #6	$209.57	3.802%	$217.5379	$217.54	$217.55	$217.50
Purchase #7	$148.45	11.475%	$165.4846	$165.48	$165.50	$165.50
7 purchase totals =	$1,029.34		$1,127.9426	$1,127.94	$1,128.00	$1,127.80