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 $96.76   8.214%   $104.7079   $104.71   $104.70   $104.70  
  Purchase #2 $224.94   5.651%   $237.6514   $237.65   $237.65   $237.70  
  Purchase #3 $76.93   8.249%   $83.276   $83.28   $83.30   $83.30  
  Purchase #4 $233.90   5.238%   $246.1517   $246.15   $246.15   $246.20  
  Purchase #5 $249.34   9.428%   $272.8478   $272.85   $272.85   $272.80  
  Purchase #6 $218.51   7.358%   $234.588   $234.59   $234.60   $234.60  
  Purchase #7 $52.57   7.354%   $56.436   $56.44   $56.45   $56.40  
  7 purchase totals = $1,152.95       $1,235.6588   $1,235.67   $1,235.70   $1,235.70