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	$150.57	7.812%	$162.3325	$162.33	$162.35	$162.30
Purchase #2	$190.54	5.325%	$200.6863	$200.69	$200.70	$200.70
Purchase #3	$44.33	4.777%	$46.4476	$46.45	$46.45	$46.40
Purchase #4	$128.73	9.758%	$141.2915	$141.29	$141.30	$141.30
Purchase #5	$164.73	7.446%	$176.9958	$177.00	$177.00	$177.00
Purchase #6	$52.78	12.269%	$59.2556	$59.26	$59.25	$59.30
Purchase #7	$201.35	3.418%	$208.2321	$208.23	$208.25	$208.20
7 purchase totals =	$933.03		$995.2414	$995.25	$995.30	$995.20