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 $58.51   4.264%   $61.0049   $61.00   $61.00   $61.00  
  Purchase #2 $66.63   9.363%   $72.8686   $72.87   $72.85   $72.90  
  Purchase #3 $197.40   4.427%   $206.1389   $206.14   $206.15   $206.10  
  Purchase #4 $93.92   12.393%   $105.5595   $105.56   $105.55   $105.60  
  Purchase #5 $222.70   7.419%   $239.2221   $239.22   $239.20   $239.20  
  Purchase #6 $168.34   4.364%   $175.6864   $175.69   $175.70   $175.70  
  Purchase #7 $154.99   10.830%   $171.7754   $171.78   $171.80   $171.80  
  7 purchase totals = $962.49       $1,032.2558   $1,032.26   $1,032.25   $1,032.30