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 $88.35   7.450%   $94.9321   $94.93   $94.95   $94.90  
  Purchase #2 $8.77   9.600%   $9.6119   $9.61   $9.60   $9.60  
  Purchase #3 $56.72   5.379%   $59.771   $59.77   $59.75   $59.80  
  Purchase #4 $61.97   8.457%   $67.2108   $67.21   $67.20   $67.20  
  Purchase #5 $102.93   10.366%   $113.5997   $113.60   $113.60   $113.60  
  Purchase #6 $182.69   10.387%   $201.666   $201.67   $201.65   $201.70  
  Purchase #7 $190.72   10.351%   $210.4614   $210.46   $210.45   $210.50  
  7 purchase totals = $692.15       $757.2529   $757.25   $757.20   $757.30