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	$127.65	3.257%	$131.8076	$131.81	$131.80	$131.80
Purchase #2	$90.37	10.669%	$100.0116	$100.01	$100.00	$100.00
Purchase #3	$49.93	5.195%	$52.5239	$52.52	$52.50	$52.50
Purchase #4	$50.83	3.166%	$52.4393	$52.44	$52.45	$52.40
Purchase #5	$140.60	9.871%	$154.4786	$154.48	$154.50	$154.50
Purchase #6	$181.70	3.518%	$188.0922	$188.09	$188.10	$188.10
Purchase #7	$156.60	10.713%	$173.3766	$173.38	$173.40	$173.40
7 purchase totals =	$797.68		$852.7298	$852.73	$852.75	$852.70