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	$136.95	11.463%	$152.6486	$152.65	$152.65	$152.60
Purchase #2	$35.86	7.705%	$38.623	$38.62	$38.60	$38.60
Purchase #3	$132.45	10.842%	$146.8102	$146.81	$146.80	$146.80
Purchase #4	$77.78	9.304%	$85.0167	$85.02	$85.00	$85.00
Purchase #5	$134.63	3.458%	$139.2855	$139.29	$139.30	$139.30
Purchase #6	$102.28	10.273%	$112.7872	$112.79	$112.80	$112.80
Purchase #7	$47.42	13.721%	$53.9265	$53.93	$53.95	$53.90
7 purchase totals =	$667.37		$729.0977	$729.11	$729.10	$729.00