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 $104.83   8.755%   $114.0079   $114.01   $114.00   $114.00  
  Purchase #2 $212.47   3.676%   $220.2804   $220.28   $220.30   $220.30  
  Purchase #3 $82.76   9.574%   $90.6834   $90.68   $90.70   $90.70  
  Purchase #4 $245.55   6.537%   $261.6016   $261.60   $261.60   $261.60  
  Purchase #5 $97.93   7.374%   $105.1514   $105.15   $105.15   $105.20  
  Purchase #6 $95.95   8.312%   $103.9254   $103.93   $103.95   $103.90  
  Purchase #7 $132.56   13.146%   $149.9863   $149.99   $150.00   $150.00  
  7 purchase totals = $972.05       $1,045.6364   $1,045.64   $1,045.70   $1,045.70