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	$67.42	7.593%	$72.5392	$72.54	$72.55	$72.50
Purchase #2	$196.81	4.260%	$205.1941	$205.19	$205.20	$205.20
Purchase #3	$164.99	9.388%	$180.4793	$180.48	$180.50	$180.50
Purchase #4	$175.83	10.672%	$194.5946	$194.59	$194.60	$194.60
Purchase #5	$128.94	12.862%	$145.5243	$145.52	$145.50	$145.50
Purchase #6	$158.78	6.227%	$168.6672	$168.67	$168.65	$168.70
Purchase #7	$158.50	11.856%	$177.2918	$177.29	$177.30	$177.30
7 purchase totals =	$1,051.27		$1,144.2905	$1,144.28	$1,144.30	$1,144.30