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	$45.68	9.321%	$49.9378	$49.94	$49.95	$49.90
Purchase #2	$192.74	6.823%	$205.8907	$205.89	$205.90	$205.90
Purchase #3	$225.26	5.267%	$237.1244	$237.12	$237.10	$237.10
Purchase #4	$190.32	5.571%	$200.9227	$200.92	$200.90	$200.90
Purchase #5	$25.38	7.536%	$27.2926	$27.29	$27.30	$27.30
Purchase #6	$86.86	8.146%	$93.9356	$93.94	$93.95	$93.90
Purchase #7	$215.76	3.126%	$222.5047	$222.50	$222.50	$222.50
7 purchase totals =	$982.00		$1,037.6085	$1,037.60	$1,037.60	$1,037.50