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	$161.43	4.616%	$168.8816	$168.88	$168.90	$168.90
Purchase #2	$189.77	3.332%	$196.0931	$196.09	$196.10	$196.10
Purchase #3	$177.53	4.682%	$185.842	$185.84	$185.85	$185.80
Purchase #4	$38.52	12.211%	$43.2237	$43.22	$43.20	$43.20
Purchase #5	$90.70	7.710%	$97.693	$97.69	$97.70	$97.70
Purchase #6	$199.41	13.299%	$225.9295	$225.93	$225.95	$225.90
Purchase #7	$37.35	4.827%	$39.1529	$39.15	$39.15	$39.20
7 purchase totals =	$894.71		$956.8158	$956.80	$956.85	$956.80