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 $188.91   6.658%   $201.4876   $201.49   $201.50   $201.50  
  Purchase #2 $229.68   5.116%   $241.4304   $241.43   $241.45   $241.40  
  Purchase #3 $136.97   3.797%   $142.1708   $142.17   $142.15   $142.20  
  Purchase #4 $178.77   12.269%   $200.7033   $200.70   $200.70   $200.70  
  Purchase #5 $132.99   6.627%   $141.8032   $141.80   $141.80   $141.80  
  Purchase #6 $36.97   6.826%   $39.4936   $39.49   $39.50   $39.50  
  Purchase #7 $43.60   13.592%   $49.5261   $49.53   $49.55   $49.50  
  7 purchase totals = $947.89       $1,016.6150   $1,016.61   $1,016.65   $1,016.60