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	$43.56	4.871%	$45.6818	$45.68	$45.70	$45.70
Purchase #2	$156.64	7.375%	$168.1922	$168.19	$168.20	$168.20
Purchase #3	$148.86	12.526%	$167.5062	$167.51	$167.50	$167.50
Purchase #4	$212.67	7.384%	$228.3736	$228.37	$228.35	$228.40
Purchase #5	$18.88	3.247%	$19.493	$19.49	$19.50	$19.50
Purchase #6	$16.89	12.659%	$19.0281	$19.03	$19.05	$19.00
Purchase #7	$166.69	11.388%	$185.6727	$185.67	$185.65	$185.70
7 purchase totals =	$764.19		$833.9476	$833.94	$833.95	$834.00