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 $227.41   8.603%   $246.9741   $246.97   $246.95   $247.00  
  Purchase #2 $186.46   5.533%   $196.7768   $196.78   $196.80   $196.80  
  Purchase #3 $79.80   8.429%   $86.5263   $86.53   $86.55   $86.50  
  Purchase #4 $173.77   3.662%   $180.1335   $180.13   $180.15   $180.10  
  Purchase #5 $26.32   3.804%   $27.3212   $27.32   $27.30   $27.30  
  Purchase #6 $236.93   13.528%   $268.9819   $268.98   $269.00   $269.00  
  Purchase #7 $118.53   3.696%   $122.9109   $122.91   $122.90   $122.90  
  7 purchase totals = $1,049.22       $1,129.6247   $1,129.62   $1,129.65   $1,129.60