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 $193.58   5.760%   $204.7302   $204.73   $204.75   $204.70  
  Purchase #2 $14.68   12.806%   $16.5599   $16.56   $16.55   $16.60  
  Purchase #3 $191.45   6.229%   $203.3754   $203.38   $203.40   $203.40  
  Purchase #4 $18.51   11.341%   $20.6092   $20.61   $20.60   $20.60  
  Purchase #5 $105.78   12.751%   $119.268   $119.27   $119.25   $119.30  
  Purchase #6 $29.61   6.698%   $31.5933   $31.59   $31.60   $31.60  
  Purchase #7 $122.66   5.557%   $129.4762   $129.48   $129.50   $129.50  
  7 purchase totals = $676.27       $725.6122   $725.62   $725.65   $725.70