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	$116.89	13.837%	$133.0641	$133.06	$133.05	$133.10
Purchase #2	$125.41	12.392%	$140.9508	$140.95	$140.95	$141.00
Purchase #3	$193.38	6.250%	$205.4663	$205.47	$205.45	$205.50
Purchase #4	$201.56	12.373%	$226.499	$226.50	$226.50	$226.50
Purchase #5	$162.61	8.733%	$176.8107	$176.81	$176.80	$176.80
Purchase #6	$139.36	8.266%	$150.8795	$150.88	$150.90	$150.90
Purchase #7	$43.61	7.388%	$46.8319	$46.83	$46.85	$46.80
7 purchase totals =	$982.82		$1,080.5023	$1,080.50	$1,080.50	$1,080.60