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 $43.67   11.409%   $48.6523   $48.65   $48.65   $48.70  
  Purchase #2 $172.83   3.613%   $179.0743   $179.07   $179.05   $179.10  
  Purchase #3 $86.77   11.393%   $96.6557   $96.66   $96.65   $96.70  
  Purchase #4 $112.81   11.737%   $126.0505   $126.05   $126.05   $126.10  
  Purchase #5 $118.87   3.204%   $122.6786   $122.68   $122.70   $122.70  
  Purchase #6 $161.73   13.130%   $182.9651   $182.97   $182.95   $183.00  
  Purchase #7 $193.54   5.553%   $204.2873   $204.29   $204.30   $204.30  
  7 purchase totals = $890.22       $960.3638   $960.37   $960.35   $960.60