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	$180.54	8.727%	$196.2957	$196.30	$196.30	$196.30
Purchase #2	$239.54	7.636%	$257.8313	$257.83	$257.85	$257.80
Purchase #3	$103.55	6.228%	$109.9991	$110.00	$110.00	$110.00
Purchase #4	$40.30	8.371%	$43.6735	$43.67	$43.65	$43.70
Purchase #5	$152.90	13.200%	$173.0828	$173.08	$173.10	$173.10
Purchase #6	$196.43	10.768%	$217.5816	$217.58	$217.60	$217.60
Purchase #7	$19.32	12.390%	$21.7137	$21.71	$21.70	$21.70
7 purchase totals =	$932.58		$1,020.1777	$1,020.17	$1,020.20	$1,020.20