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	$177.39	12.437%	$199.452	$199.45	$199.45	$199.50
Purchase #2	$41.72	13.668%	$47.4223	$47.42	$47.40	$47.40
Purchase #3	$40.86	11.576%	$45.59	$45.59	$45.60	$45.60
Purchase #4	$90.36	13.719%	$102.7565	$102.76	$102.75	$102.80
Purchase #5	$228.78	3.378%	$236.5082	$236.51	$236.50	$236.50
Purchase #6	$10.67	6.593%	$11.3735	$11.37	$11.35	$11.40
Purchase #7	$205.77	8.537%	$223.3366	$223.34	$223.35	$223.30
7 purchase totals =	$795.55		$866.4391	$866.44	$866.40	$866.50