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 $243.82   7.468%   $262.0285   $262.03   $262.05   $262.00  
  Purchase #2 $46.75   13.438%   $53.0323   $53.03   $53.05   $53.00  
  Purchase #3 $177.65   10.589%   $196.4614   $196.46   $196.45   $196.50  
  Purchase #4 $23.62   11.618%   $26.3642   $26.36   $26.35   $26.40  
  Purchase #5 $233.81   11.710%   $261.1892   $261.19   $261.20   $261.20  
  Purchase #6 $239.37   10.271%   $263.9557   $263.96   $263.95   $264.00  
  Purchase #7 $168.74   7.713%   $181.7549   $181.75   $181.75   $181.80  
  7 purchase totals = $1,133.76       $1,244.7862   $1,244.78   $1,244.80   $1,244.90