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	$232.91	6.468%	$247.9746	$247.97	$247.95	$248.00
Purchase #2	$127.51	11.742%	$142.4822	$142.48	$142.50	$142.50
Purchase #3	$34.28	10.599%	$37.9133	$37.91	$37.90	$37.90
Purchase #4	$138.31	4.485%	$144.5132	$144.51	$144.50	$144.50
Purchase #5	$118.52	11.111%	$131.6888	$131.69	$131.70	$131.70
Purchase #6	$204.88	3.767%	$212.5978	$212.60	$212.60	$212.60
Purchase #7	$14.41	8.619%	$15.652	$15.65	$15.65	$15.70
7 purchase totals =	$870.82		$932.8219	$932.81	$932.80	$932.90