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	$212.64	8.697%	$231.1333	$231.13	$231.15	$231.10
Purchase #2	$214.53	3.658%	$222.3775	$222.38	$222.40	$222.40
Purchase #3	$142.97	11.188%	$158.9655	$158.97	$158.95	$159.00
Purchase #4	$190.27	9.790%	$208.8974	$208.90	$208.90	$208.90
Purchase #5	$23.57	5.468%	$24.8588	$24.86	$24.85	$24.90
Purchase #6	$82.54	9.664%	$90.5167	$90.52	$90.50	$90.50
Purchase #7	$88.79	9.291%	$97.0395	$97.04	$97.05	$97.00
7 purchase totals =	$955.31		$1,033.7887	$1,033.80	$1,033.80	$1,033.80