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 $47.96   10.231%   $52.8668   $52.87   $52.85   $52.90  
  Purchase #2 $193.56   4.131%   $201.556   $201.56   $201.55   $201.60  
  Purchase #3 $85.94   10.517%   $94.9783   $94.98   $95.00   $95.00  
  Purchase #4 $148.45   5.430%   $156.5108   $156.51   $156.50   $156.50  
  Purchase #5 $93.80   3.615%   $97.1909   $97.19   $97.20   $97.20  
  Purchase #6 $158.99   12.713%   $179.2024   $179.20   $179.20   $179.20  
  Purchase #7 $23.92   3.605%   $24.7823   $24.78   $24.80   $24.80  
  7 purchase totals = $752.62       $807.0875   $807.09   $807.10   $807.20