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	$165.70	3.117%	$170.8649	$170.86	$170.85	$170.90
Purchase #2	$118.40	8.588%	$128.5682	$128.57	$128.55	$128.60
Purchase #3	$165.50	13.521%	$187.8773	$187.88	$187.90	$187.90
Purchase #4	$193.62	5.188%	$203.665	$203.67	$203.65	$203.70
Purchase #5	$127.37	3.557%	$131.9006	$131.90	$131.90	$131.90
Purchase #6	$87.27	12.275%	$97.9824	$97.98	$98.00	$98.00
Purchase #7	$117.57	8.458%	$127.5141	$127.51	$127.50	$127.50
7 purchase totals =	$975.43		$1,048.3725	$1,048.37	$1,048.35	$1,048.50