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	$11.97	4.139%	$12.4654	$12.47	$12.45	$12.50
Purchase #2	$18.40	9.603%	$20.167	$20.17	$20.15	$20.20
Purchase #3	$69.98	4.856%	$73.3782	$73.38	$73.40	$73.40
Purchase #4	$82.96	8.752%	$90.2207	$90.22	$90.20	$90.20
Purchase #5	$63.49	13.111%	$71.8142	$71.81	$71.80	$71.80
Purchase #6	$24.56	3.808%	$25.4952	$25.50	$25.50	$25.50
Purchase #7	$143.66	6.684%	$153.2622	$153.26	$153.25	$153.30
7 purchase totals =	$415.02		$446.8029	$446.81	$446.75	$446.90