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	$118.40	11.471%	$131.9817	$131.98	$132.00	$132.00
Purchase #2	$81.67	4.537%	$85.3754	$85.38	$85.40	$85.40
Purchase #3	$215.52	7.141%	$230.9103	$230.91	$230.90	$230.90
Purchase #4	$143.50	9.319%	$156.8728	$156.87	$156.85	$156.90
Purchase #5	$137.43	10.299%	$151.5839	$151.58	$151.60	$151.60
Purchase #6	$26.60	12.502%	$29.9255	$29.93	$29.95	$29.90
Purchase #7	$192.89	13.638%	$219.1963	$219.20	$219.20	$219.20
7 purchase totals =	$916.01		$1,005.8459	$1,005.85	$1,005.90	$1,005.90