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 $76.38   8.577%   $82.9311   $82.93   $82.95   $82.90  
  Purchase #2 $246.77   10.774%   $273.357   $273.36   $273.35   $273.40  
  Purchase #3 $91.89   5.279%   $96.7409   $96.74   $96.75   $96.70  
  Purchase #4 $60.63   11.713%   $67.7316   $67.73   $67.75   $67.70  
  Purchase #5 $228.82   5.850%   $242.206   $242.21   $242.20   $242.20  
  Purchase #6 $186.46   6.535%   $198.6452   $198.65   $198.65   $198.60  
  Purchase #7 $186.93   10.642%   $206.8231   $206.82   $206.80   $206.80  
  7 purchase totals = $1,077.88       $1,168.4349   $1,168.44   $1,168.45   $1,168.30