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	$217.40	9.235%	$237.4769	$237.48	$237.50	$237.50
Purchase #2	$193.68	4.263%	$201.9366	$201.94	$201.95	$201.90
Purchase #3	$41.28	4.506%	$43.1401	$43.14	$43.15	$43.10
Purchase #4	$221.48	5.241%	$233.0878	$233.09	$233.10	$233.10
Purchase #5	$29.54	11.234%	$32.8585	$32.86	$32.85	$32.90
Purchase #6	$225.60	10.770%	$249.8971	$249.90	$249.90	$249.90
Purchase #7	$90.91	11.739%	$101.5819	$101.58	$101.60	$101.60
7 purchase totals =	$1,019.89		$1,099.9789	$1,099.99	$1,100.05	$1,100.00