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	$33.87	7.625%	$36.4526	$36.45	$36.45	$36.50
Purchase #2	$144.48	9.601%	$158.3515	$158.35	$158.35	$158.40
Purchase #3	$47.43	3.748%	$49.2077	$49.21	$49.20	$49.20
Purchase #4	$101.39	12.488%	$114.0516	$114.05	$114.05	$114.10
Purchase #5	$179.71	11.723%	$200.7774	$200.78	$200.80	$200.80
Purchase #6	$86.66	3.286%	$89.5076	$89.51	$89.50	$89.50
Purchase #7	$13.31	6.213%	$14.137	$14.14	$14.15	$14.10
7 purchase totals =	$606.85		$662.4854	$662.49	$662.50	$662.60