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	$100.59	4.444%	$105.0602	$105.06	$105.05	$105.10
Purchase #2	$232.66	3.591%	$241.0148	$241.01	$241.00	$241.00
Purchase #3	$170.43	3.745%	$176.8126	$176.81	$176.80	$176.80
Purchase #4	$5.73	13.705%	$6.5153	$6.52	$6.50	$6.50
Purchase #5	$64.35	12.562%	$72.4336	$72.43	$72.45	$72.40
Purchase #6	$58.65	11.257%	$65.2522	$65.25	$65.25	$65.30
Purchase #7	$11.60	10.166%	$12.7793	$12.78	$12.80	$12.80
7 purchase totals =	$644.01		$679.8680	$679.86	$679.85	$679.90