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 $119.73   4.403%   $125.0017   $125.00   $125.00   $125.00  
  Purchase #2 $168.68   13.483%   $191.4231   $191.42   $191.40   $191.40  
  Purchase #3 $98.27   8.475%   $106.5984   $106.60   $106.60   $106.60  
  Purchase #4 $67.81   7.386%   $72.8184   $72.82   $72.80   $72.80  
  Purchase #5 $242.49   6.859%   $259.1224   $259.12   $259.10   $259.10  
  Purchase #6 $129.54   13.531%   $147.0681   $147.07   $147.05   $147.10  
  Purchase #7 $227.79   3.281%   $235.2638   $235.26   $235.25   $235.30  
  7 purchase totals = $1,054.31       $1,137.2959   $1,137.29   $1,137.20   $1,137.30