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 $206.50   10.119%   $227.3957   $227.40   $227.40   $227.40  
  Purchase #2 $11.46   13.713%   $13.0315   $13.03   $13.05   $13.00  
  Purchase #3 $181.73   8.781%   $197.6877   $197.69   $197.70   $197.70  
  Purchase #4 $62.93   7.592%   $67.7076   $67.71   $67.70   $67.70  
  Purchase #5 $68.66   3.289%   $70.9182   $70.92   $70.90   $70.90  
  Purchase #6 $244.44   7.206%   $262.0543   $262.05   $262.05   $262.10  
  Purchase #7 $245.56   7.336%   $263.5743   $263.57   $263.55   $263.60  
  7 purchase totals = $1,021.28       $1,102.3693   $1,102.37   $1,102.35   $1,102.40