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	$10.90	9.489%	$11.9343	$11.93	$11.95	$11.90
Purchase #2	$40.38	8.556%	$43.8349	$43.83	$43.85	$43.80
Purchase #3	$167.78	4.400%	$175.1623	$175.16	$175.15	$175.20
Purchase #4	$194.57	10.528%	$215.0543	$215.05	$215.05	$215.10
Purchase #5	$11.81	5.777%	$12.4923	$12.49	$12.50	$12.50
Purchase #6	$189.63	7.624%	$204.0874	$204.09	$204.10	$204.10
Purchase #7	$110.95	11.680%	$123.909	$123.91	$123.90	$123.90
7 purchase totals =	$726.02		$786.4745	$786.46	$786.50	$786.50