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	$174.63	12.676%	$196.7661	$196.77	$196.75	$196.80
Purchase #2	$185.72	12.119%	$208.2274	$208.23	$208.25	$208.20
Purchase #3	$157.69	13.514%	$179.0002	$179.00	$179.00	$179.00
Purchase #4	$179.70	5.775%	$190.0777	$190.08	$190.10	$190.10
Purchase #5	$206.59	8.675%	$224.5117	$224.51	$224.50	$224.50
Purchase #6	$240.58	7.425%	$258.4431	$258.44	$258.45	$258.40
Purchase #7	$20.94	12.612%	$23.581	$23.58	$23.60	$23.60
7 purchase totals =	$1,165.85		$1,280.6072	$1,280.61	$1,280.65	$1,280.60