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	$68.88	10.581%	$76.1682	$76.17	$76.15	$76.20
Purchase #2	$150.46	5.548%	$158.8075	$158.81	$158.80	$158.80
Purchase #3	$36.34	10.390%	$40.1157	$40.12	$40.10	$40.10
Purchase #4	$174.88	13.766%	$198.954	$198.95	$198.95	$199.00
Purchase #5	$145.61	7.158%	$156.0328	$156.03	$156.05	$156.00
Purchase #6	$248.85	8.615%	$270.2884	$270.29	$270.30	$270.30
Purchase #7	$100.38	12.711%	$113.1393	$113.14	$113.15	$113.10
7 purchase totals =	$925.40		$1,013.5059	$1,013.51	$1,013.50	$1,013.50