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 $193.69   11.353%   $215.6796   $215.68   $215.70   $215.70  
  Purchase #2 $104.67   5.836%   $110.7785   $110.78   $110.80   $110.80  
  Purchase #3 $130.94   10.611%   $144.834   $144.83   $144.85   $144.80  
  Purchase #4 $167.63   8.186%   $181.3522   $181.35   $181.35   $181.40  
  Purchase #5 $169.80   3.295%   $175.3949   $175.39   $175.40   $175.40  
  Purchase #6 $54.81   9.583%   $60.0624   $60.06   $60.05   $60.10  
  Purchase #7 $235.97   4.337%   $246.204   $246.20   $246.20   $246.20  
  7 purchase totals = $1,057.51       $1,134.3056   $1,134.29   $1,134.35   $1,134.40