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 $92.59   4.527%   $96.7815   $96.78   $96.80   $96.80  
  Purchase #2 $95.31   8.339%   $103.2579   $103.26   $103.25   $103.30  
  Purchase #3 $9.70   11.137%   $10.7803   $10.78   $10.80   $10.80  
  Purchase #4 $40.25   8.405%   $43.633   $43.63   $43.65   $43.60  
  Purchase #5 $51.35   13.723%   $58.3968   $58.40   $58.40   $58.40  
  Purchase #6 $122.79   11.328%   $136.6997   $136.70   $136.70   $136.70  
  Purchase #7 $22.32   9.150%   $24.3623   $24.36   $24.35   $24.40  
  7 purchase totals = $434.31       $473.9115   $473.91   $473.95   $474.00