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 $241.61   7.506%   $259.7452   $259.75   $259.75   $259.70  
  Purchase #2 $153.46   13.279%   $173.838   $173.84   $173.85   $173.80  
  Purchase #3 $115.36   3.622%   $119.5383   $119.54   $119.55   $119.50  
  Purchase #4 $183.37   13.221%   $207.6133   $207.61   $207.60   $207.60  
  Purchase #5 $234.86   12.217%   $263.5528   $263.55   $263.55   $263.60  
  Purchase #6 $179.61   4.524%   $187.7356   $187.74   $187.75   $187.70  
  Purchase #7 $222.56   3.111%   $229.4838   $229.48   $229.50   $229.50  
  7 purchase totals = $1,330.83       $1,441.5070   $1,441.51   $1,441.55   $1,441.40