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	$41.25	13.699%	$46.9008	$46.90	$46.90	$46.90
Purchase #2	$224.75	6.243%	$238.7811	$238.78	$238.80	$238.80
Purchase #3	$87.50	11.569%	$97.6229	$97.62	$97.60	$97.60
Purchase #4	$178.70	7.417%	$191.9542	$191.95	$191.95	$192.00
Purchase #5	$222.54	8.211%	$240.8128	$240.81	$240.80	$240.80
Purchase #6	$47.37	9.656%	$51.944	$51.94	$51.95	$51.90
Purchase #7	$136.91	10.820%	$151.7237	$151.72	$151.70	$151.70
7 purchase totals =	$939.02		$1,019.7395	$1,019.72	$1,019.70	$1,019.70