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 $68.69   11.372%   $76.5014   $76.50   $76.50   $76.50  
  Purchase #2 $85.83   9.378%   $93.8791   $93.88   $93.90   $93.90  
  Purchase #3 $160.83   6.196%   $170.795   $170.80   $170.80   $170.80  
  Purchase #4 $175.68   10.549%   $194.2125   $194.21   $194.20   $194.20  
  Purchase #5 $244.34   3.764%   $253.537   $253.54   $253.55   $253.50  
  Purchase #6 $16.63   10.863%   $18.4365   $18.44   $18.45   $18.40  
  Purchase #7 $125.29   11.628%   $139.8587   $139.86   $139.85   $139.90  
  7 purchase totals = $877.29       $947.2202   $947.23   $947.25   $947.20