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	$147.50	8.733%	$160.3812	$160.38	$160.40	$160.40
Purchase #2	$173.83	10.707%	$192.442	$192.44	$192.45	$192.40
Purchase #3	$199.35	5.223%	$209.7621	$209.76	$209.75	$209.80
Purchase #4	$38.79	10.376%	$42.8149	$42.81	$42.80	$42.80
Purchase #5	$223.95	6.628%	$238.7934	$238.79	$238.80	$238.80
Purchase #6	$215.73	6.387%	$229.5087	$229.51	$229.50	$229.50
Purchase #7	$200.38	6.689%	$213.7834	$213.78	$213.80	$213.80
7 purchase totals =	$1,199.53		$1,287.4857	$1,287.47	$1,287.50	$1,287.50