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 $92.65   6.715%   $98.8714   $98.87   $98.85   $98.90  
  Purchase #2 $115.25   7.134%   $123.4719   $123.47   $123.45   $123.50  
  Purchase #3 $61.25   13.587%   $69.572   $69.57   $69.55   $69.60  
  Purchase #4 $86.78   12.584%   $97.7004   $97.70   $97.70   $97.70  
  Purchase #5 $205.89   11.849%   $230.2859   $230.29   $230.30   $230.30  
  Purchase #6 $59.99   3.636%   $62.1712   $62.17   $62.15   $62.20  
  Purchase #7 $241.52   12.593%   $271.9346   $271.93   $271.95   $271.90  
  7 purchase totals = $863.33       $954.0074   $954.00   $953.95   $954.10