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 $195.81   3.160%   $201.9976   $202.00   $202.00   $202.00  
  Purchase #2 $25.33   3.527%   $26.2234   $26.22   $26.20   $26.20  
  Purchase #3 $221.78   13.769%   $252.3169   $252.32   $252.30   $252.30  
  Purchase #4 $236.75   13.242%   $268.1004   $268.10   $268.10   $268.10  
  Purchase #5 $95.73   7.666%   $103.0687   $103.07   $103.05   $103.10  
  Purchase #6 $227.92   13.313%   $258.263   $258.26   $258.25   $258.30  
  Purchase #7 $32.56   3.276%   $33.6267   $33.63   $33.65   $33.60  
  7 purchase totals = $1,035.88       $1,143.5967   $1,143.60   $1,143.55   $1,143.60