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	$160.98	10.473%	$177.8394	$177.84	$177.85	$177.80
Purchase #2	$58.81	11.383%	$65.5043	$65.50	$65.50	$65.50
Purchase #3	$14.67	12.282%	$16.4718	$16.47	$16.45	$16.50
Purchase #4	$131.99	13.655%	$150.0132	$150.01	$150.00	$150.00
Purchase #5	$28.86	11.141%	$32.0753	$32.08	$32.10	$32.10
Purchase #6	$40.74	5.305%	$42.9013	$42.90	$42.90	$42.90
Purchase #7	$104.31	7.102%	$111.7181	$111.72	$111.70	$111.70
7 purchase totals =	$540.36		$596.5234	$596.52	$596.50	$596.50