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	$69.57	11.692%	$77.7041	$77.70	$77.70	$77.70
Purchase #2	$81.82	4.822%	$85.7654	$85.77	$85.75	$85.80
Purchase #3	$96.47	8.779%	$104.9391	$104.94	$104.95	$104.90
Purchase #4	$29.47	5.719%	$31.1554	$31.16	$31.15	$31.20
Purchase #5	$180.35	11.400%	$200.9099	$200.91	$200.90	$200.90
Purchase #6	$54.59	3.406%	$56.4493	$56.45	$56.45	$56.40
Purchase #7	$146.96	9.296%	$160.6214	$160.62	$160.60	$160.60
7 purchase totals =	$659.23		$717.5446	$717.55	$717.50	$717.50