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 $182.48   9.442%   $199.7098   $199.71   $199.70   $199.70  
  Purchase #2 $195.26   13.593%   $221.8017   $221.80   $221.80   $221.80  
  Purchase #3 $102.26   9.157%   $111.6239   $111.62   $111.60   $111.60  
  Purchase #4 $193.53   4.612%   $202.4556   $202.46   $202.45   $202.50  
  Purchase #5 $221.86   12.488%   $249.5659   $249.57   $249.55   $249.60  
  Purchase #6 $232.97   4.254%   $242.8805   $242.88   $242.90   $242.90  
  Purchase #7 $35.51   11.265%   $39.5102   $39.51   $39.50   $39.50  
  7 purchase totals = $1,163.87       $1,267.5476   $1,267.55   $1,267.50   $1,267.60