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	$207.49	13.235%	$234.9513	$234.95	$234.95	$235.00
Purchase #2	$199.85	7.388%	$214.6149	$214.61	$214.60	$214.60
Purchase #3	$205.55	6.800%	$219.5274	$219.53	$219.55	$219.50
Purchase #4	$78.96	13.835%	$89.8841	$89.88	$89.90	$89.90
Purchase #5	$90.58	9.147%	$98.8654	$98.87	$98.85	$98.90
Purchase #6	$192.89	13.694%	$219.3044	$219.30	$219.30	$219.30
Purchase #7	$193.55	3.511%	$200.3455	$200.35	$200.35	$200.30
7 purchase totals =	$1,168.87		$1,277.4930	$1,277.49	$1,277.50	$1,277.50