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 $112.95   5.815%   $119.518   $119.52   $119.50   $119.50  
  Purchase #2 $217.39   12.217%   $243.9485   $243.95   $243.95   $243.90  
  Purchase #3 $165.78   3.147%   $170.9971   $171.00   $171.00   $171.00  
  Purchase #4 $250.53   10.490%   $276.8106   $276.81   $276.80   $276.80  
  Purchase #5 $138.85   13.669%   $157.8294   $157.83   $157.85   $157.80  
  Purchase #6 $62.99   13.381%   $71.4187   $71.42   $71.40   $71.40  
  Purchase #7 $143.85   12.172%   $161.3594   $161.36   $161.35   $161.40  
  7 purchase totals = $1,092.34       $1,201.8817   $1,201.89   $1,201.85   $1,201.80