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 $209.78   11.604%   $234.1229   $234.12   $234.10   $234.10  
  Purchase #2 $216.64   9.389%   $236.9803   $236.98   $237.00   $237.00  
  Purchase #3 $55.95   9.418%   $61.2194   $61.22   $61.20   $61.20  
  Purchase #4 $216.85   13.852%   $246.8881   $246.89   $246.90   $246.90  
  Purchase #5 $118.61   13.755%   $134.9248   $134.92   $134.90   $134.90  
  Purchase #6 $85.32   12.380%   $95.8826   $95.88   $95.90   $95.90  
  Purchase #7 $5.54   12.799%   $6.2491   $6.25   $6.25   $6.20  
  7 purchase totals = $908.69       $1,016.2672   $1,016.26   $1,016.25   $1,016.20