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	$190.39	5.384%	$200.6406	$200.64	$200.65	$200.60
Purchase #2	$36.95	10.336%	$40.7692	$40.77	$40.75	$40.80
Purchase #3	$45.80	8.339%	$49.6193	$49.62	$49.60	$49.60
Purchase #4	$148.35	11.102%	$164.8198	$164.82	$164.80	$164.80
Purchase #5	$76.88	6.677%	$82.0133	$82.01	$82.00	$82.00
Purchase #6	$92.70	3.559%	$95.9992	$96.00	$96.00	$96.00
Purchase #7	$137.45	6.844%	$146.8571	$146.86	$146.85	$146.90
7 purchase totals =	$728.52		$780.7185	$780.72	$780.65	$780.70