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 $83.54   4.552%   $87.3427   $87.34   $87.35   $87.30  
  Purchase #2 $201.56   6.272%   $214.2018   $214.20   $214.20   $214.20  
  Purchase #3 $40.63   10.397%   $44.8543   $44.85   $44.85   $44.90  
  Purchase #4 $205.79   13.708%   $233.9997   $234.00   $234.00   $234.00  
  Purchase #5 $165.56   5.612%   $174.8512   $174.85   $174.85   $174.90  
  Purchase #6 $246.65   6.168%   $261.8634   $261.86   $261.85   $261.90  
  Purchase #7 $72.47   8.599%   $78.7017   $78.70   $78.70   $78.70  
  7 purchase totals = $1,016.20       $1,095.8148   $1,095.80   $1,095.80   $1,095.90