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	$32.28	7.511%	$34.7046	$34.70	$34.70	$34.70
Purchase #2	$19.54	8.117%	$21.1261	$21.13	$21.15	$21.10
Purchase #3	$174.64	4.252%	$182.0657	$182.07	$182.05	$182.10
Purchase #4	$13.57	11.524%	$15.1338	$15.13	$15.15	$15.10
Purchase #5	$186.67	13.843%	$212.5107	$212.51	$212.50	$212.50
Purchase #6	$77.78	7.296%	$83.4548	$83.45	$83.45	$83.50
Purchase #7	$148.59	4.665%	$155.5217	$155.52	$155.50	$155.50
7 purchase totals =	$653.07		$704.5174	$704.51	$704.50	$704.50