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 $233.41   12.218%   $261.928   $261.93   $261.95   $261.90  
  Purchase #2 $233.66   8.161%   $252.729   $252.73   $252.75   $252.70  
  Purchase #3 $42.73   8.476%   $46.3518   $46.35   $46.35   $46.40  
  Purchase #4 $165.85   13.424%   $188.1137   $188.11   $188.10   $188.10  
  Purchase #5 $120.60   4.374%   $125.875   $125.88   $125.90   $125.90  
  Purchase #6 $126.34   12.234%   $141.7964   $141.80   $141.80   $141.80  
  Purchase #7 $12.93   6.207%   $13.7326   $13.73   $13.75   $13.70  
  7 purchase totals = $935.52       $1,030.5265   $1,030.53   $1,030.60   $1,030.50