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 $246.87   6.558%   $263.0597   $263.06   $263.05   $263.10  
  Purchase #2 $136.31   10.461%   $150.5694   $150.57   $150.55   $150.60  
  Purchase #3 $98.32   6.665%   $104.873   $104.87   $104.85   $104.90  
  Purchase #4 $142.99   3.740%   $148.3378   $148.34   $148.35   $148.30  
  Purchase #5 $197.41   8.483%   $214.1563   $214.16   $214.15   $214.20  
  Purchase #6 $192.97   7.614%   $207.6627   $207.66   $207.65   $207.70  
  Purchase #7 $52.59   6.846%   $56.1903   $56.19   $56.20   $56.20  
  7 purchase totals = $1,067.46       $1,144.8492   $1,144.85   $1,144.80   $1,145.00