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 $76.55   12.283%   $85.9526   $85.95   $85.95   $86.00  
  Purchase #2 $230.86   7.619%   $248.4492   $248.45   $248.45   $248.40  
  Purchase #3 $24.85   4.378%   $25.9379   $25.94   $25.95   $25.90  
  Purchase #4 $97.32   6.817%   $103.9543   $103.95   $103.95   $104.00  
  Purchase #5 $103.67   11.592%   $115.6874   $115.69   $115.70   $115.70  
  Purchase #6 $215.62   5.266%   $226.9745   $226.97   $226.95   $227.00  
  Purchase #7 $50.86   5.412%   $53.6125   $53.61   $53.60   $53.60  
  7 purchase totals = $799.73       $860.5684   $860.56   $860.55   $860.60