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 $176.98   9.659%   $194.0745   $194.07   $194.05   $194.10  
  Purchase #2 $25.93   11.856%   $29.0043   $29.00   $29.00   $29.00  
  Purchase #3 $201.37   6.223%   $213.9013   $213.90   $213.90   $213.90  
  Purchase #4 $64.30   11.665%   $71.8006   $71.80   $71.80   $71.80  
  Purchase #5 $93.69   4.135%   $97.5641   $97.56   $97.55   $97.60  
  Purchase #6 $20.76   13.601%   $23.5836   $23.58   $23.60   $23.60  
  Purchase #7 $211.80   10.455%   $233.9437   $233.94   $233.95   $233.90  
  7 purchase totals = $794.83       $863.8721   $863.85   $863.85   $863.90