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	$65.83	9.122%	$71.835	$71.84	$71.85	$71.80
Purchase #2	$103.41	7.652%	$111.3229	$111.32	$111.30	$111.30
Purchase #3	$56.69	11.622%	$63.2785	$63.28	$63.30	$63.30
Purchase #4	$157.45	13.866%	$179.282	$179.28	$179.30	$179.30
Purchase #5	$161.48	10.727%	$178.802	$178.80	$178.80	$178.80
Purchase #6	$42.30	6.414%	$45.0131	$45.01	$45.00	$45.00
Purchase #7	$32.53	5.758%	$34.4031	$34.40	$34.40	$34.40
7 purchase totals =	$619.69		$683.9366	$683.93	$683.95	$683.90