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 $119.26   5.552%   $125.8813   $125.88   $125.90   $125.90  
  Purchase #2 $181.31   12.628%   $204.2058   $204.21   $204.20   $204.20  
  Purchase #3 $201.47   13.157%   $227.9774   $227.98   $228.00   $228.00  
  Purchase #4 $96.25   12.187%   $107.98   $107.98   $108.00   $108.00  
  Purchase #5 $146.37   7.799%   $157.7854   $157.79   $157.80   $157.80  
  Purchase #6 $171.77   9.597%   $188.2548   $188.25   $188.25   $188.30  
  Purchase #7 $8.39   10.231%   $9.2484   $9.25   $9.25   $9.20  
  7 purchase totals = $924.82       $1,021.3331   $1,021.34   $1,021.40   $1,021.40