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 $65.95   11.630%   $73.62   $73.62   $73.60   $73.60  
  Purchase #2 $157.51   13.699%   $179.0873   $179.09   $179.10   $179.10  
  Purchase #3 $134.52   11.419%   $149.8808   $149.88   $149.90   $149.90  
  Purchase #4 $30.80   9.622%   $33.7636   $33.76   $33.75   $33.80  
  Purchase #5 $201.66   7.389%   $216.5607   $216.56   $216.55   $216.60  
  Purchase #6 $53.35   5.381%   $56.2208   $56.22   $56.20   $56.20  
  Purchase #7 $228.93   5.341%   $241.1572   $241.16   $241.15   $241.20  
  7 purchase totals = $872.72       $950.2904   $950.29   $950.25   $950.40