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	$81.30	5.544%	$85.8073	$85.81	$85.80	$85.80
Purchase #2	$18.72	12.639%	$21.086	$21.09	$21.10	$21.10
Purchase #3	$65.82	11.444%	$73.3524	$73.35	$73.35	$73.40
Purchase #4	$107.47	8.298%	$116.3879	$116.39	$116.40	$116.40
Purchase #5	$59.75	9.395%	$65.3635	$65.36	$65.35	$65.40
Purchase #6	$98.82	11.115%	$109.8038	$109.80	$109.80	$109.80
Purchase #7	$39.92	6.352%	$42.4557	$42.46	$42.45	$42.50
7 purchase totals =	$471.80		$514.2566	$514.26	$514.25	$514.40