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	$100.64	10.691%	$111.3994	$111.40	$111.40	$111.40
Purchase #2	$178.58	10.203%	$196.8005	$196.80	$196.80	$196.80
Purchase #3	$213.40	11.395%	$237.7169	$237.72	$237.70	$237.70
Purchase #4	$211.82	10.571%	$234.2115	$234.21	$234.20	$234.20
Purchase #5	$45.47	9.583%	$49.8274	$49.83	$49.85	$49.80
Purchase #6	$140.89	8.121%	$152.3317	$152.33	$152.35	$152.30
Purchase #7	$193.79	7.618%	$208.5529	$208.55	$208.55	$208.60
7 purchase totals =	$1,084.59		$1,190.8403	$1,190.84	$1,190.85	$1,190.80