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	$29.43	10.482%	$32.5149	$32.51	$32.50	$32.50
Purchase #2	$35.40	5.293%	$37.2737	$37.27	$37.25	$37.30
Purchase #3	$152.66	10.427%	$168.5779	$168.58	$168.60	$168.60
Purchase #4	$190.62	12.731%	$214.8878	$214.89	$214.90	$214.90
Purchase #5	$116.64	5.306%	$122.8289	$122.83	$122.85	$122.80
Purchase #6	$48.83	4.786%	$51.167	$51.17	$51.15	$51.20
Purchase #7	$93.96	9.642%	$103.0196	$103.02	$103.00	$103.00
7 purchase totals =	$667.54		$730.2698	$730.27	$730.25	$730.30