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 $243.62   8.490%   $264.3033   $264.30   $264.30   $264.30  
  Purchase #2 $76.93   6.411%   $81.862   $81.86   $81.85   $81.90  
  Purchase #3 $86.92   8.782%   $94.5533   $94.55   $94.55   $94.60  
  Purchase #4 $220.31   11.420%   $245.4694   $245.47   $245.45   $245.50  
  Purchase #5 $202.65   6.276%   $215.3683   $215.37   $215.35   $215.40  
  Purchase #6 $95.79   9.240%   $104.641   $104.64   $104.65   $104.60  
  Purchase #7 $176.84   11.217%   $196.6761   $196.68   $196.70   $196.70  
  7 purchase totals = $1,103.06       $1,202.8734   $1,202.87   $1,202.85   $1,203.00