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	$98.94	4.350%	$103.2439	$103.24	$103.25	$103.20
Purchase #2	$127.58	11.404%	$142.1292	$142.13	$142.15	$142.10
Purchase #3	$82.80	11.699%	$92.4868	$92.49	$92.50	$92.50
Purchase #4	$236.28	8.617%	$256.6402	$256.64	$256.65	$256.60
Purchase #5	$232.60	5.120%	$244.5091	$244.51	$244.50	$244.50
Purchase #6	$63.49	7.846%	$68.4714	$68.47	$68.45	$68.50
Purchase #7	$28.95	8.777%	$31.4909	$31.49	$31.50	$31.50
7 purchase totals =	$870.64		$938.9715	$938.97	$939.00	$938.90