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	$127.60	5.681%	$134.849	$134.85	$134.85	$134.80
Purchase #2	$238.70	11.209%	$265.4559	$265.46	$265.45	$265.50
Purchase #3	$69.94	3.118%	$72.1207	$72.12	$72.10	$72.10
Purchase #4	$27.57	5.323%	$29.0376	$29.04	$29.05	$29.00
Purchase #5	$154.71	10.223%	$170.526	$170.53	$170.55	$170.50
Purchase #6	$133.89	12.126%	$150.1255	$150.13	$150.15	$150.10
Purchase #7	$238.55	5.491%	$251.6488	$251.65	$251.65	$251.60
7 purchase totals =	$990.96		$1,073.7635	$1,073.78	$1,073.80	$1,073.60