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 $84.32   9.290%   $92.1533   $92.15   $92.15   $92.20  
  Purchase #2 $105.52   3.537%   $109.2522   $109.25   $109.25   $109.30  
  Purchase #3 $198.27   4.701%   $207.5907   $207.59   $207.60   $207.60  
  Purchase #4 $245.45   5.667%   $259.3597   $259.36   $259.35   $259.40  
  Purchase #5 $234.46   3.485%   $242.6309   $242.63   $242.65   $242.60  
  Purchase #6 $35.60   5.629%   $37.6039   $37.60   $37.60   $37.60  
  Purchase #7 $202.91   9.615%   $222.4198   $222.42   $222.40   $222.40  
  7 purchase totals = $1,106.53       $1,171.0105   $1,171.00   $1,171.00   $1,171.10