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 $44.32   8.348%   $48.0198   $48.02   $48.00   $48.00  
  Purchase #2 $169.63   9.142%   $185.1376   $185.14   $185.15   $185.10  
  Purchase #3 $74.56   12.238%   $83.6847   $83.68   $83.70   $83.70  
  Purchase #4 $179.78   8.604%   $195.2483   $195.25   $195.25   $195.20  
  Purchase #5 $108.60   5.590%   $114.6707   $114.67   $114.65   $114.70  
  Purchase #6 $205.98   3.868%   $213.9473   $213.95   $213.95   $213.90  
  Purchase #7 $55.52   4.378%   $57.9507   $57.95   $57.95   $58.00  
  7 purchase totals = $838.39       $898.6591   $898.66   $898.65   $898.60