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	$12.34	12.598%	$13.8946	$13.89	$13.90	$13.90
Purchase #2	$78.99	5.758%	$83.5382	$83.54	$83.55	$83.50
Purchase #3	$223.44	8.264%	$241.9051	$241.91	$241.90	$241.90
Purchase #4	$32.37	5.648%	$34.1983	$34.20	$34.20	$34.20
Purchase #5	$51.74	5.540%	$54.6064	$54.61	$54.60	$54.60
Purchase #6	$13.46	7.546%	$14.4757	$14.48	$14.50	$14.50
Purchase #7	$18.40	11.768%	$20.5653	$20.57	$20.55	$20.60
7 purchase totals =	$430.74		$463.1836	$463.20	$463.20	$463.20