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	$182.59	4.172%	$190.2077	$190.21	$190.20	$190.20
Purchase #2	$52.63	9.492%	$57.6256	$57.63	$57.65	$57.60
Purchase #3	$143.76	8.865%	$156.5043	$156.50	$156.50	$156.50
Purchase #4	$133.65	12.695%	$150.6169	$150.62	$150.60	$150.60
Purchase #5	$63.38	10.195%	$69.8416	$69.84	$69.85	$69.80
Purchase #6	$50.37	11.803%	$56.3152	$56.32	$56.30	$56.30
Purchase #7	$111.76	6.809%	$119.3697	$119.37	$119.35	$119.40
7 purchase totals =	$738.14		$800.4810	$800.49	$800.45	$800.40