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	$36.73	5.763%	$38.8467	$38.85	$38.85	$38.80
Purchase #2	$7.38	5.507%	$7.7864	$7.79	$7.80	$7.80
Purchase #3	$21.60	10.650%	$23.9004	$23.90	$23.90	$23.90
Purchase #4	$35.45	11.626%	$39.5714	$39.57	$39.55	$39.60
Purchase #5	$17.76	13.538%	$20.1643	$20.16	$20.15	$20.20
Purchase #6	$43.75	5.309%	$46.0727	$46.07	$46.05	$46.10
Purchase #7	$127.54	9.354%	$139.4701	$139.47	$139.45	$139.50
7 purchase totals =	$290.21		$315.8120	$315.81	$315.75	$315.90