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 $230.70   5.662%   $243.7622   $243.76   $243.75   $243.80  
  Purchase #2 $110.99   9.164%   $121.1611   $121.16   $121.15   $121.20  
  Purchase #3 $72.53   7.534%   $77.9944   $77.99   $78.00   $78.00  
  Purchase #4 $190.61   3.478%   $197.2394   $197.24   $197.25   $197.20  
  Purchase #5 $236.86   4.679%   $247.9427   $247.94   $247.95   $247.90  
  Purchase #6 $246.73   13.778%   $280.7245   $280.72   $280.70   $280.70  
  Purchase #7 $29.61   10.184%   $32.6255   $32.63   $32.65   $32.60  
  7 purchase totals = $1,118.03       $1,201.4498   $1,201.44   $1,201.45   $1,201.40