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	$187.52	4.727%	$196.3841	$196.38	$196.40	$196.40
Purchase #2	$120.52	12.413%	$135.4801	$135.48	$135.50	$135.50
Purchase #3	$133.84	4.306%	$139.6032	$139.60	$139.60	$139.60
Purchase #4	$139.99	7.509%	$150.5018	$150.50	$150.50	$150.50
Purchase #5	$70.73	3.843%	$73.4482	$73.45	$73.45	$73.40
Purchase #6	$126.37	8.379%	$136.9585	$136.96	$136.95	$137.00
Purchase #7	$57.98	7.733%	$62.4636	$62.46	$62.45	$62.50
7 purchase totals =	$836.95		$894.8395	$894.83	$894.85	$894.90