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 $93.25   8.793%   $101.4495   $101.45   $101.45   $101.40  
  Purchase #2 $250.65   4.188%   $261.1472   $261.15   $261.15   $261.10  
  Purchase #3 $127.60   3.358%   $131.8848   $131.88   $131.90   $131.90  
  Purchase #4 $125.67   8.229%   $136.0114   $136.01   $136.00   $136.00  
  Purchase #5 $184.79   9.428%   $202.212   $202.21   $202.20   $202.20  
  Purchase #6 $243.88   6.813%   $260.4955   $260.50   $260.50   $260.50  
  Purchase #7 $93.34   10.583%   $103.2182   $103.22   $103.20   $103.20  
  7 purchase totals = $1,119.18       $1,196.4186   $1,196.42   $1,196.40   $1,196.30