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	$183.89	5.535%	$194.0683	$194.07	$194.05	$194.10
Purchase #2	$108.82	9.447%	$119.1002	$119.10	$119.10	$119.10
Purchase #3	$131.96	13.765%	$150.1243	$150.12	$150.10	$150.10
Purchase #4	$80.67	11.193%	$89.6994	$89.70	$89.70	$89.70
Purchase #5	$83.45	7.628%	$89.8156	$89.82	$89.80	$89.80
Purchase #6	$195.51	6.800%	$208.8047	$208.80	$208.80	$208.80
Purchase #7	$9.59	4.186%	$9.9914	$9.99	$10.00	$10.00
7 purchase totals =	$793.89		$861.6039	$861.60	$861.55	$861.60