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	$47.86	9.425%	$52.3708	$52.37	$52.35	$52.40
Purchase #2	$143.99	11.138%	$160.0276	$160.03	$160.05	$160.00
Purchase #3	$55.65	9.472%	$60.9212	$60.92	$60.90	$60.90
Purchase #4	$151.82	11.754%	$169.6649	$169.66	$169.65	$169.70
Purchase #5	$101.88	3.209%	$105.1493	$105.15	$105.15	$105.10
Purchase #6	$87.59	7.726%	$94.3572	$94.36	$94.35	$94.40
Purchase #7	$52.80	13.421%	$59.8863	$59.89	$59.90	$59.90
7 purchase totals =	$641.59		$702.3773	$702.38	$702.35	$702.40