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 $178.82   9.236%   $195.3358   $195.34   $195.35   $195.30  
  Purchase #2 $114.59   6.512%   $122.0521   $122.05   $122.05   $122.10  
  Purchase #3 $64.71   9.203%   $70.6653   $70.67   $70.65   $70.70  
  Purchase #4 $227.39   13.805%   $258.7812   $258.78   $258.80   $258.80  
  Purchase #5 $207.57   9.801%   $227.9139   $227.91   $227.90   $227.90  
  Purchase #6 $15.70   11.853%   $17.5609   $17.56   $17.55   $17.60  
  Purchase #7 $150.45   3.721%   $156.0482   $156.05   $156.05   $156.00  
  7 purchase totals = $959.23       $1,048.3574   $1,048.36   $1,048.35   $1,048.40