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	$126.86	13.266%	$143.6892	$143.69	$143.70	$143.70
Purchase #2	$208.68	9.778%	$229.0847	$229.08	$229.10	$229.10
Purchase #3	$198.45	13.822%	$225.8798	$225.88	$225.90	$225.90
Purchase #4	$80.56	12.382%	$90.5349	$90.53	$90.55	$90.50
Purchase #5	$136.81	9.681%	$150.0546	$150.05	$150.05	$150.10
Purchase #6	$147.26	6.815%	$157.2958	$157.30	$157.30	$157.30
Purchase #7	$137.85	5.686%	$145.6882	$145.69	$145.70	$145.70
7 purchase totals =	$1,036.47		$1,142.2272	$1,142.22	$1,142.30	$1,142.30