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	$216.75	3.703%	$224.7763	$224.78	$224.80	$224.80
Purchase #2	$20.39	5.619%	$21.5357	$21.54	$21.55	$21.50
Purchase #3	$143.90	4.351%	$150.1611	$150.16	$150.15	$150.20
Purchase #4	$37.49	11.817%	$41.9202	$41.92	$41.90	$41.90
Purchase #5	$46.37	5.254%	$48.8063	$48.81	$48.80	$48.80
Purchase #6	$25.78	9.863%	$28.3227	$28.32	$28.30	$28.30
Purchase #7	$45.72	6.559%	$48.7188	$48.72	$48.70	$48.70
7 purchase totals =	$536.40		$564.2411	$564.25	$564.20	$564.20