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	$163.91	7.383%	$176.0115	$176.01	$176.00	$176.00
Purchase #2	$182.43	9.710%	$200.144	$200.14	$200.15	$200.10
Purchase #3	$104.82	4.858%	$109.9122	$109.91	$109.90	$109.90
Purchase #4	$132.71	4.637%	$138.8638	$138.86	$138.85	$138.90
Purchase #5	$44.43	3.265%	$45.8806	$45.88	$45.90	$45.90
Purchase #6	$203.88	12.584%	$229.5363	$229.54	$229.55	$229.50
Purchase #7	$165.84	4.643%	$173.54	$173.54	$173.55	$173.50
7 purchase totals =	$998.02		$1,073.8884	$1,073.88	$1,073.90	$1,073.80