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 $211.66   5.229%   $222.7277   $222.73   $222.75   $222.70  
  Purchase #2 $221.54   3.139%   $228.4941   $228.49   $228.50   $228.50  
  Purchase #3 $52.56   5.318%   $55.3551   $55.36   $55.35   $55.40  
  Purchase #4 $248.40   3.441%   $256.9474   $256.95   $256.95   $256.90  
  Purchase #5 $245.78   12.459%   $276.4017   $276.40   $276.40   $276.40  
  Purchase #6 $214.27   5.500%   $226.0549   $226.05   $226.05   $226.10  
  Purchase #7 $243.54   5.668%   $257.3438   $257.34   $257.35   $257.30  
  7 purchase totals = $1,437.75       $1,523.3247   $1,523.32   $1,523.35   $1,523.30