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	$250.47	10.441%	$276.6216	$276.62	$276.60	$276.60
Purchase #2	$136.30	3.656%	$141.2831	$141.28	$141.30	$141.30
Purchase #3	$211.59	8.198%	$228.9361	$228.94	$228.95	$228.90
Purchase #4	$152.57	10.531%	$168.6371	$168.64	$168.65	$168.60
Purchase #5	$34.34	11.267%	$38.2091	$38.21	$38.20	$38.20
Purchase #6	$164.43	7.271%	$176.3857	$176.39	$176.40	$176.40
Purchase #7	$48.43	6.570%	$51.6119	$51.61	$51.60	$51.60
7 purchase totals =	$998.13		$1,081.6846	$1,081.69	$1,081.70	$1,081.60