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	$147.84	13.344%	$167.5678	$167.57	$167.55	$167.60
Purchase #2	$177.40	10.149%	$195.4043	$195.40	$195.40	$195.40
Purchase #3	$34.56	3.616%	$35.8097	$35.81	$35.80	$35.80
Purchase #4	$86.25	11.164%	$95.879	$95.88	$95.90	$95.90
Purchase #5	$12.46	13.105%	$14.0929	$14.09	$14.10	$14.10
Purchase #6	$82.37	12.723%	$92.8499	$92.85	$92.85	$92.80
Purchase #7	$139.25	12.238%	$156.2914	$156.29	$156.30	$156.30
7 purchase totals =	$680.13		$757.8950	$757.89	$757.90	$757.90