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	$176.43	13.443%	$200.1475	$200.15	$200.15	$200.10
Purchase #2	$237.57	10.171%	$261.7332	$261.73	$261.75	$261.70
Purchase #3	$153.79	9.767%	$168.8107	$168.81	$168.80	$168.80
Purchase #4	$47.28	4.731%	$49.5168	$49.52	$49.50	$49.50
Purchase #5	$116.73	8.800%	$127.0022	$127.00	$127.00	$127.00
Purchase #6	$119.92	3.337%	$123.9217	$123.92	$123.90	$123.90
Purchase #7	$122.30	12.179%	$137.1949	$137.19	$137.20	$137.20
7 purchase totals =	$974.02		$1,068.3270	$1,068.32	$1,068.30	$1,068.20