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	$246.78	13.864%	$280.9936	$280.99	$281.00	$281.00
Purchase #2	$76.86	5.471%	$81.065	$81.07	$81.05	$81.10
Purchase #3	$30.38	8.208%	$32.8736	$32.87	$32.85	$32.90
Purchase #4	$229.87	11.314%	$255.8775	$255.88	$255.90	$255.90
Purchase #5	$57.99	8.474%	$62.9041	$62.90	$62.90	$62.90
Purchase #6	$108.78	13.525%	$123.4925	$123.49	$123.50	$123.50
Purchase #7	$176.42	5.371%	$185.8955	$185.90	$185.90	$185.90
7 purchase totals =	$927.08		$1,023.1018	$1,023.10	$1,023.10	$1,023.20