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	$137.35	13.177%	$155.4486	$155.45	$155.45	$155.40
Purchase #2	$22.42	3.648%	$23.2379	$23.24	$23.25	$23.20
Purchase #3	$56.42	10.792%	$62.5088	$62.51	$62.50	$62.50
Purchase #4	$161.42	6.363%	$171.6912	$171.69	$171.70	$171.70
Purchase #5	$127.51	13.393%	$144.5874	$144.59	$144.60	$144.60
Purchase #6	$165.63	13.528%	$188.0364	$188.04	$188.05	$188.00
Purchase #7	$42.41	9.628%	$46.4932	$46.49	$46.50	$46.50
7 purchase totals =	$713.16		$792.0035	$792.01	$792.05	$791.90