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 $73.69   3.735%   $76.4423   $76.44   $76.45   $76.40  
  Purchase #2 $181.62   13.837%   $206.7508   $206.75   $206.75   $206.80  
  Purchase #3 $237.78   11.759%   $265.7406   $265.74   $265.75   $265.70  
  Purchase #4 $110.64   12.778%   $124.7776   $124.78   $124.80   $124.80  
  Purchase #5 $119.33   5.352%   $125.7165   $125.72   $125.70   $125.70  
  Purchase #6 $117.37   7.575%   $126.2608   $126.26   $126.25   $126.30  
  Purchase #7 $30.89   7.666%   $33.258   $33.26   $33.25   $33.30  
  7 purchase totals = $871.32       $958.9466   $958.95   $958.95   $959.00