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 $58.86   7.812%   $63.4581   $63.46   $63.45   $63.50  
  Purchase #2 $21.95   3.589%   $22.7378   $22.74   $22.75   $22.70  
  Purchase #3 $164.76   3.281%   $170.1658   $170.17   $170.15   $170.20  
  Purchase #4 $227.70   6.690%   $242.9331   $242.93   $242.95   $242.90  
  Purchase #5 $177.56   8.400%   $192.475   $192.48   $192.50   $192.50  
  Purchase #6 $243.40   6.326%   $258.7975   $258.80   $258.80   $258.80  
  Purchase #7 $207.73   11.526%   $231.673   $231.67   $231.65   $231.70  
  7 purchase totals = $1,101.96       $1,182.2403   $1,182.25   $1,182.25   $1,182.30