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	$11.37	13.210%	$12.872	$12.87	$12.85	$12.90
Purchase #2	$17.37	8.335%	$18.8178	$18.82	$18.80	$18.80
Purchase #3	$10.41	3.829%	$10.8086	$10.81	$10.80	$10.80
Purchase #4	$33.74	13.316%	$38.2328	$38.23	$38.25	$38.20
Purchase #5	$34.97	11.673%	$39.052	$39.05	$39.05	$39.10
Purchase #6	$56.95	5.134%	$59.8738	$59.87	$59.85	$59.90
Purchase #7	$211.69	12.747%	$238.6741	$238.67	$238.65	$238.70
7 purchase totals =	$376.50		$418.3311	$418.32	$418.25	$418.40