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 $207.94   8.650%   $225.9268   $225.93   $225.95   $225.90  
  Purchase #2 $149.67   9.290%   $163.5743   $163.57   $163.55   $163.60  
  Purchase #3 $56.77   9.132%   $61.9542   $61.95   $61.95   $62.00  
  Purchase #4 $130.64   8.280%   $141.457   $141.46   $141.45   $141.50  
  Purchase #5 $144.25   3.607%   $149.4531   $149.45   $149.45   $149.50  
  Purchase #6 $181.39   8.109%   $196.0989   $196.10   $196.10   $196.10  
  Purchase #7 $78.79   9.772%   $86.4894   $86.49   $86.50   $86.50  
  7 purchase totals = $949.45       $1,024.9537   $1,024.95   $1,024.95   $1,025.10