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	$36.51	10.387%	$40.3023	$40.30	$40.30	$40.30
Purchase #2	$17.29	10.729%	$19.145	$19.15	$19.15	$19.10
Purchase #3	$206.85	7.285%	$221.919	$221.92	$221.90	$221.90
Purchase #4	$39.89	13.518%	$45.2823	$45.28	$45.30	$45.30
Purchase #5	$94.48	6.661%	$100.7733	$100.77	$100.75	$100.80
Purchase #6	$208.54	6.491%	$222.0763	$222.08	$222.10	$222.10
Purchase #7	$113.32	5.605%	$119.6716	$119.67	$119.65	$119.70
7 purchase totals =	$716.88		$769.1698	$769.17	$769.15	$769.20