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 $190.70   5.792%   $201.7453   $201.75   $201.75   $201.70  
  Purchase #2 $163.99   10.417%   $181.0728   $181.07   $181.05   $181.10  
  Purchase #3 $126.42   5.513%   $133.3895   $133.39   $133.40   $133.40  
  Purchase #4 $234.38   4.555%   $245.056   $245.06   $245.05   $245.10  
  Purchase #5 $170.82   3.465%   $176.7389   $176.74   $176.75   $176.70  
  Purchase #6 $44.28   5.283%   $46.6193   $46.62   $46.60   $46.60  
  Purchase #7 $246.66   5.236%   $259.5751   $259.58   $259.60   $259.60  
  7 purchase totals = $1,177.25       $1,244.1969   $1,244.21   $1,244.20   $1,244.20