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 $167.43   5.208%   $176.1498   $176.15   $176.15   $176.10  
  Purchase #2 $49.43   8.495%   $53.6291   $53.63   $53.65   $53.60  
  Purchase #3 $249.30   5.524%   $263.0713   $263.07   $263.05   $263.10  
  Purchase #4 $13.28   3.410%   $13.7328   $13.73   $13.75   $13.70  
  Purchase #5 $120.54   11.305%   $134.167   $134.17   $134.15   $134.20  
  Purchase #6 $166.39   12.182%   $186.6596   $186.66   $186.65   $186.70  
  Purchase #7 $189.83   7.252%   $203.5965   $203.60   $203.60   $203.60  
  7 purchase totals = $956.20       $1,031.0061   $1,031.01   $1,031.00   $1,031.00