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	$101.55	9.305%	$110.9992	$111.00	$111.00	$111.00
Purchase #2	$169.25	12.395%	$190.2285	$190.23	$190.25	$190.20
Purchase #3	$35.70	11.642%	$39.8562	$39.86	$39.85	$39.90
Purchase #4	$180.97	5.170%	$190.3261	$190.33	$190.35	$190.30
Purchase #5	$13.64	7.617%	$14.679	$14.68	$14.70	$14.70
Purchase #6	$138.79	9.682%	$152.2276	$152.23	$152.25	$152.20
Purchase #7	$239.57	6.824%	$255.9183	$255.92	$255.90	$255.90
7 purchase totals =	$879.47		$954.2349	$954.25	$954.30	$954.20