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	$33.85	4.848%	$35.491	$35.49	$35.50	$35.50
Purchase #2	$132.89	9.599%	$145.6461	$145.65	$145.65	$145.60
Purchase #3	$175.64	11.591%	$195.9984	$196.00	$196.00	$196.00
Purchase #4	$207.91	10.151%	$229.0149	$229.01	$229.00	$229.00
Purchase #5	$55.78	10.222%	$61.4818	$61.48	$61.50	$61.50
Purchase #6	$47.38	11.715%	$52.9306	$52.93	$52.95	$52.90
Purchase #7	$190.40	12.851%	$214.8683	$214.87	$214.85	$214.90
7 purchase totals =	$843.85		$935.4311	$935.43	$935.45	$935.40