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 $208.36   11.871%   $233.0944   $233.09   $233.10   $233.10  
  Purchase #2 $121.52   3.268%   $125.4913   $125.49   $125.50   $125.50  
  Purchase #3 $234.76   10.856%   $260.2455   $260.25   $260.25   $260.20  
  Purchase #4 $232.30   9.631%   $254.6728   $254.67   $254.65   $254.70  
  Purchase #5 $166.81   8.317%   $180.6836   $180.68   $180.70   $180.70  
  Purchase #6 $59.27   11.688%   $66.1975   $66.20   $66.20   $66.20  
  Purchase #7 $43.43   7.268%   $46.5865   $46.59   $46.60   $46.60  
  7 purchase totals = $1,066.45       $1,166.9716   $1,166.97   $1,167.00   $1,167.00