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	$32.35	3.216%	$33.3904	$33.39	$33.40	$33.40
Purchase #2	$143.61	4.598%	$150.2132	$150.21	$150.20	$150.20
Purchase #3	$236.44	10.386%	$260.9967	$261.00	$261.00	$261.00
Purchase #4	$228.72	5.499%	$241.2973	$241.30	$241.30	$241.30
Purchase #5	$241.35	6.132%	$256.1496	$256.15	$256.15	$256.10
Purchase #6	$219.45	5.643%	$231.8336	$231.83	$231.85	$231.80
Purchase #7	$40.81	5.500%	$43.0546	$43.05	$43.05	$43.10
7 purchase totals =	$1,142.73		$1,216.9354	$1,216.93	$1,216.95	$1,216.90