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 $143.64   5.826%   $152.0085   $152.01   $152.00   $152.00  
  Purchase #2 $16.70   10.547%   $18.4613   $18.46   $18.45   $18.50  
  Purchase #3 $195.74   3.144%   $201.8941   $201.89   $201.90   $201.90  
  Purchase #4 $187.54   5.586%   $198.016   $198.02   $198.00   $198.00  
  Purchase #5 $146.84   11.803%   $164.1715   $164.17   $164.15   $164.20  
  Purchase #6 $85.99   8.596%   $93.3817   $93.38   $93.40   $93.40  
  Purchase #7 $176.73   13.838%   $201.1859   $201.19   $201.20   $201.20  
  7 purchase totals = $953.18       $1,029.1190   $1,029.12   $1,029.10   $1,029.20