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	$226.31	11.223%	$251.7088	$251.71	$251.70	$251.70
Purchase #2	$39.93	5.200%	$42.0064	$42.01	$42.00	$42.00
Purchase #3	$173.32	13.474%	$196.6731	$196.67	$196.65	$196.70
Purchase #4	$91.45	7.461%	$98.2731	$98.27	$98.25	$98.30
Purchase #5	$242.78	5.295%	$255.6352	$255.64	$255.65	$255.60
Purchase #6	$198.29	13.637%	$225.3308	$225.33	$225.35	$225.30
Purchase #7	$15.66	10.280%	$17.2698	$17.27	$17.25	$17.30
7 purchase totals =	$987.74		$1,086.8972	$1,086.90	$1,086.85	$1,086.90