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	$186.48	5.449%	$196.6413	$196.64	$196.65	$196.60
Purchase #2	$232.47	11.446%	$259.0785	$259.08	$259.10	$259.10
Purchase #3	$123.76	10.484%	$136.735	$136.74	$136.75	$136.70
Purchase #4	$112.66	4.760%	$118.0226	$118.02	$118.00	$118.00
Purchase #5	$34.94	7.579%	$37.5881	$37.59	$37.60	$37.60
Purchase #6	$182.83	12.518%	$205.7167	$205.72	$205.70	$205.70
Purchase #7	$12.36	12.688%	$13.9282	$13.93	$13.95	$13.90
7 purchase totals =	$885.50		$967.7104	$967.72	$967.75	$967.60