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 $119.53   4.617%   $125.0487   $125.05   $125.05   $125.00  
  Purchase #2 $217.35   11.154%   $241.5932   $241.59   $241.60   $241.60  
  Purchase #3 $120.37   4.218%   $125.4472   $125.45   $125.45   $125.40  
  Purchase #4 $179.33   5.228%   $188.7054   $188.71   $188.70   $188.70  
  Purchase #5 $107.81   10.155%   $118.7581   $118.76   $118.75   $118.80  
  Purchase #6 $102.59   4.601%   $107.3102   $107.31   $107.30   $107.30  
  Purchase #7 $202.56   8.756%   $220.2962   $220.30   $220.30   $220.30  
  7 purchase totals = $1,049.54       $1,127.1590   $1,127.17   $1,127.15   $1,127.10