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	$112.97	3.393%	$116.8031	$116.80	$116.80	$116.80
Purchase #2	$75.68	5.732%	$80.018	$80.02	$80.00	$80.00
Purchase #3	$147.75	8.253%	$159.9438	$159.94	$159.95	$159.90
Purchase #4	$132.81	3.111%	$136.9417	$136.94	$136.95	$136.90
Purchase #5	$86.39	4.800%	$90.5367	$90.54	$90.55	$90.50
Purchase #6	$136.78	6.760%	$146.0263	$146.03	$146.05	$146.00
Purchase #7	$185.80	6.776%	$198.3898	$198.39	$198.40	$198.40
7 purchase totals =	$878.18		$928.6594	$928.66	$928.70	$928.50