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 $152.54   5.553%   $161.0105   $161.01   $161.00   $161.00  
  Purchase #2 $247.45   3.530%   $256.185   $256.19   $256.20   $256.20  
  Purchase #3 $204.37   5.710%   $216.0395   $216.04   $216.05   $216.00  
  Purchase #4 $147.66   3.798%   $153.2681   $153.27   $153.25   $153.30  
  Purchase #5 $188.97   5.588%   $199.5296   $199.53   $199.55   $199.50  
  Purchase #6 $68.85   10.320%   $75.9553   $75.96   $75.95   $76.00  
  Purchase #7 $164.96   13.655%   $187.4853   $187.49   $187.50   $187.50  
  7 purchase totals = $1,174.80       $1,249.4733   $1,249.49   $1,249.50   $1,249.50