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	$57.89	12.468%	$65.1077	$65.11	$65.10	$65.10
Purchase #2	$6.82	11.290%	$7.59	$7.59	$7.60	$7.60
Purchase #3	$9.46	9.675%	$10.3753	$10.38	$10.40	$10.40
Purchase #4	$177.57	8.620%	$192.8765	$192.88	$192.90	$192.90
Purchase #5	$203.64	5.616%	$215.0764	$215.08	$215.10	$215.10
Purchase #6	$40.53	3.725%	$42.0397	$42.04	$42.05	$42.00
Purchase #7	$65.69	10.580%	$72.64	$72.64	$72.65	$72.60
7 purchase totals =	$561.60		$605.7056	$605.72	$605.80	$605.70