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	$194.38	13.853%	$221.3075	$221.31	$221.30	$221.30
Purchase #2	$232.43	4.257%	$242.3245	$242.32	$242.30	$242.30
Purchase #3	$31.55	9.725%	$34.6182	$34.62	$34.60	$34.60
Purchase #4	$85.98	7.743%	$92.6374	$92.64	$92.65	$92.60
Purchase #5	$246.77	13.347%	$279.7064	$279.71	$279.70	$279.70
Purchase #6	$63.29	12.262%	$71.0506	$71.05	$71.05	$71.10
Purchase #7	$212.50	4.720%	$222.53	$222.53	$222.55	$222.50
7 purchase totals =	$1,066.90		$1,164.1746	$1,164.18	$1,164.15	$1,164.10