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 $71.38   5.282%   $75.1503   $75.15   $75.15   $75.20  
  Purchase #2 $204.29   11.269%   $227.3114   $227.31   $227.30   $227.30  
  Purchase #3 $180.75   4.593%   $189.0518   $189.05   $189.05   $189.10  
  Purchase #4 $24.98   4.462%   $26.0946   $26.09   $26.10   $26.10  
  Purchase #5 $217.50   8.677%   $236.3725   $236.37   $236.35   $236.40  
  Purchase #6 $122.97   13.127%   $139.1123   $139.11   $139.10   $139.10  
  Purchase #7 $185.76   9.313%   $203.0598   $203.06   $203.05   $203.10  
  7 purchase totals = $1,007.63       $1,096.1527   $1,096.14   $1,096.10   $1,096.30