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 $44.88   8.195%   $48.5579   $48.56   $48.55   $48.60  
  Purchase #2 $205.87   10.629%   $227.7519   $227.75   $227.75   $227.80  
  Purchase #3 $78.26   8.713%   $85.0788   $85.08   $85.10   $85.10  
  Purchase #4 $170.55   6.481%   $181.6033   $181.60   $181.60   $181.60  
  Purchase #5 $157.94   8.150%   $170.8121   $170.81   $170.80   $170.80  
  Purchase #6 $138.33   11.363%   $154.0484   $154.05   $154.05   $154.00  
  Purchase #7 $190.94   4.511%   $199.5533   $199.55   $199.55   $199.60  
  7 purchase totals = $986.77       $1,067.4057   $1,067.40   $1,067.40   $1,067.50