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 $112.82   10.862%   $125.0745   $125.07   $125.05   $125.10  
  Purchase #2 $159.68   10.731%   $176.8153   $176.82   $176.80   $176.80  
  Purchase #3 $25.26   4.833%   $26.4808   $26.48   $26.50   $26.50  
  Purchase #4 $191.36   12.644%   $215.5556   $215.56   $215.55   $215.60  
  Purchase #5 $161.39   6.285%   $171.5334   $171.53   $171.55   $171.50  
  Purchase #6 $85.75   9.129%   $93.5781   $93.58   $93.60   $93.60  
  Purchase #7 $178.55   4.413%   $186.4294   $186.43   $186.45   $186.40  
  7 purchase totals = $914.81       $995.4671   $995.47   $995.50   $995.50