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	$162.46	9.260%	$177.5038	$177.50	$177.50	$177.50
Purchase #2	$150.64	8.142%	$162.9051	$162.91	$162.90	$162.90
Purchase #3	$102.85	8.831%	$111.9327	$111.93	$111.95	$111.90
Purchase #4	$126.98	10.514%	$140.3307	$140.33	$140.35	$140.30
Purchase #5	$111.95	7.262%	$120.0798	$120.08	$120.10	$120.10
Purchase #6	$127.30	12.441%	$143.1374	$143.14	$143.15	$143.10
Purchase #7	$63.80	10.208%	$70.3127	$70.31	$70.30	$70.30
7 purchase totals =	$845.98		$926.2022	$926.20	$926.25	$926.10