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 $195.94   9.578%   $214.7071   $214.71   $214.70   $214.70  
  Purchase #2 $234.71   11.468%   $261.6265   $261.63   $261.65   $261.60  
  Purchase #3 $49.84   4.342%   $52.0041   $52.00   $52.00   $52.00  
  Purchase #4 $197.32   11.756%   $220.5169   $220.52   $220.50   $220.50  
  Purchase #5 $151.52   10.823%   $167.919   $167.92   $167.90   $167.90  
  Purchase #6 $121.80   11.347%   $135.6206   $135.62   $135.60   $135.60  
  Purchase #7 $10.45   11.856%   $11.689   $11.69   $11.70   $11.70  
  7 purchase totals = $961.58       $1,064.0832   $1,064.09   $1,064.05   $1,064.00