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 $46.84   6.607%   $49.9347   $49.93   $49.95   $49.90  
  Purchase #2 $65.97   8.720%   $71.7226   $71.72   $71.70   $71.70  
  Purchase #3 $62.97   7.527%   $67.7098   $67.71   $67.70   $67.70  
  Purchase #4 $213.61   4.379%   $222.964   $222.96   $222.95   $223.00  
  Purchase #5 $127.39   8.347%   $138.0232   $138.02   $138.00   $138.00  
  Purchase #6 $80.70   3.460%   $83.4922   $83.49   $83.50   $83.50  
  Purchase #7 $114.25   11.370%   $127.2402   $127.24   $127.25   $127.20  
  7 purchase totals = $711.73       $761.0867   $761.07   $761.05   $761.00