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	$204.78	9.431%	$224.0928	$224.09	$224.10	$224.10
Purchase #2	$128.47	8.651%	$139.5839	$139.58	$139.60	$139.60
Purchase #3	$79.61	13.315%	$90.2101	$90.21	$90.20	$90.20
Purchase #4	$69.60	4.426%	$72.6805	$72.68	$72.70	$72.70
Purchase #5	$67.66	7.218%	$72.5437	$72.54	$72.55	$72.50
Purchase #6	$151.67	8.654%	$164.7955	$164.80	$164.80	$164.80
Purchase #7	$250.68	4.124%	$261.018	$261.02	$261.00	$261.00
7 purchase totals =	$952.47		$1,024.9245	$1,024.92	$1,024.95	$1,024.90