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	$65.32	11.459%	$72.805	$72.81	$72.80	$72.80
Purchase #2	$76.69	4.574%	$80.1978	$80.20	$80.20	$80.20
Purchase #3	$60.79	11.763%	$67.9407	$67.94	$67.95	$67.90
Purchase #4	$10.66	9.266%	$11.6478	$11.65	$11.65	$11.60
Purchase #5	$130.39	6.659%	$139.0727	$139.07	$139.05	$139.10
Purchase #6	$67.76	4.609%	$70.8831	$70.88	$70.90	$70.90
Purchase #7	$175.76	9.129%	$191.8051	$191.81	$191.80	$191.80
7 purchase totals =	$587.37		$634.3522	$634.36	$634.35	$634.30