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	$110.60	3.109%	$114.0386	$114.04	$114.05	$114.00
Purchase #2	$25.83	10.417%	$28.5207	$28.52	$28.50	$28.50
Purchase #3	$150.59	10.193%	$165.9396	$165.94	$165.95	$165.90
Purchase #4	$123.92	6.387%	$131.8348	$131.83	$131.85	$131.80
Purchase #5	$36.53	4.269%	$38.0895	$38.09	$38.10	$38.10
Purchase #6	$58.53	12.616%	$65.9141	$65.91	$65.90	$65.90
Purchase #7	$140.65	10.580%	$155.5308	$155.53	$155.55	$155.50
7 purchase totals =	$646.65		$699.8681	$699.86	$699.90	$699.70