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	$12.96	12.439%	$14.5721	$14.57	$14.55	$14.60
Purchase #2	$205.61	12.577%	$231.4696	$231.47	$231.45	$231.50
Purchase #3	$173.86	13.274%	$196.9382	$196.94	$196.95	$196.90
Purchase #4	$136.64	13.409%	$154.9621	$154.96	$154.95	$155.00
Purchase #5	$99.74	11.329%	$111.0395	$111.04	$111.05	$111.00
Purchase #6	$207.77	11.615%	$231.9025	$231.90	$231.90	$231.90
Purchase #7	$196.34	6.362%	$208.8312	$208.83	$208.85	$208.80
7 purchase totals =	$1,032.92		$1,149.7152	$1,149.71	$1,149.70	$1,149.70