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 $63.55   5.455%   $67.0167   $67.02   $67.00   $67.00  
  Purchase #2 $212.40   8.265%   $229.9549   $229.95   $229.95   $230.00  
  Purchase #3 $118.70   6.846%   $126.8262   $126.83   $126.85   $126.80  
  Purchase #4 $51.69   12.318%   $58.0572   $58.06   $58.05   $58.10  
  Purchase #5 $170.95   6.501%   $182.0635   $182.06   $182.05   $182.10  
  Purchase #6 $245.94   12.711%   $277.2014   $277.20   $277.20   $277.20  
  Purchase #7 $68.34   11.105%   $75.9292   $75.93   $75.95   $75.90  
  7 purchase totals = $931.57       $1,017.0491   $1,017.05   $1,017.05   $1,017.10