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 $208.25   9.367%   $227.7568   $227.76   $227.75   $227.80  
  Purchase #2 $43.84   10.560%   $48.4695   $48.47   $48.45   $48.50  
  Purchase #3 $243.60   3.521%   $252.1772   $252.18   $252.20   $252.20  
  Purchase #4 $242.32   4.262%   $252.6477   $252.65   $252.65   $252.60  
  Purchase #5 $132.54   3.253%   $136.8515   $136.85   $136.85   $136.90  
  Purchase #6 $33.31   6.415%   $35.4468   $35.45   $35.45   $35.40  
  Purchase #7 $160.59   12.209%   $180.1964   $180.20   $180.20   $180.20  
  7 purchase totals = $1,064.45       $1,133.5459   $1,133.56   $1,133.55   $1,133.60