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 $204.25   3.314%   $211.0188   $211.02   $211.00   $211.00  
  Purchase #2 $25.72   5.366%   $27.1001   $27.10   $27.10   $27.10  
  Purchase #3 $237.62   8.617%   $258.0957   $258.10   $258.10   $258.10  
  Purchase #4 $238.46   3.188%   $246.0621   $246.06   $246.05   $246.10  
  Purchase #5 $74.86   9.561%   $82.0174   $82.02   $82.00   $82.00  
  Purchase #6 $96.65   8.374%   $104.7435   $104.74   $104.75   $104.70  
  Purchase #7 $170.44   7.228%   $182.7594   $182.76   $182.75   $182.80  
  7 purchase totals = $1,048.00       $1,111.7970   $1,111.80   $1,111.75   $1,111.80