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	$127.88	4.172%	$133.2152	$133.22	$133.20	$133.20
Purchase #2	$130.52	11.534%	$145.5742	$145.57	$145.55	$145.60
Purchase #3	$239.43	9.448%	$262.0513	$262.05	$262.05	$262.10
Purchase #4	$9.76	11.611%	$10.8932	$10.89	$10.90	$10.90
Purchase #5	$198.85	11.855%	$222.4237	$222.42	$222.40	$222.40
Purchase #6	$99.96	13.768%	$113.7225	$113.72	$113.70	$113.70
Purchase #7	$142.39	10.157%	$156.8526	$156.85	$156.85	$156.90
7 purchase totals =	$948.79		$1,044.7327	$1,044.72	$1,044.65	$1,044.80